Controlling cyclone efficiency with a vacuum interface

ABSTRACT

Powder overspray that is extracted from a spray booth is recovered back to a powder supply that is used to supply powder to the spray guns inside the spray booth. The powder overspray extracted from the booth is separated from the high flow air stream by a separator such as a cyclone separator. The powder falls into a transfer pan and a vacuum is used to convey the powder from the transfer pan to a vacuum receiver. The powder is then discharged to the feed hopper in the feed center. The use of a vacuum to convey powder from the cyclone to the feed center in effect permits substantially all of the powder overspray to be recovered from the spray booth directly to the feed hopper with minimal dwell or residence time within the cyclone or vacuum receiver subsystems during a spraying operation. The receiver can be rotated for easy cleaning, and the vacuum line cleaned by one or more cleaning elements drawn through the vacuum line.

RELATED APPLICATIONS

The present application claims the benefit of pending U.S. provisionalpatent application Ser. No. 60/290,447 filed on May 11, 2001 forCONTROLLING CYCLONE EFFICIENCY WITH A VACUUM INTERFACE the entiredisclosure of which is fully incorporated herein by reference. Thepresent application is a continuation-in-part of pending U.S. patentapplication Ser. No. 09/888,679 filed on Jun. 25, 2001 for QUICK CHANGEPOWDER COATING SPRAY SYSTEM which claims the benefit of U.S. Provisionalpatent application Ser. Nos. 60/277,149 filed on Mar. 19, 2001, and60/238,277 filed on Oct. 5, 2000, the entire disclosures of which arefully incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates generally to powder coating spray systems whichuse powder containment spray booths and power overspray recoveryapparatus. More particularly, the invention relates to a powder coatingspray system that uses negative pressure to influence cyclone efficiencyby increasing the yield of powder particles recovered from the cyclone.

BACKGROUND OF THE INVENTION

Powder coatings are commonly applied to objects by powder spray gunsthat may be manually operated or automatic. In an automatic system, oneor more spray guns are controlled to spray powder onto the objects asthe objects are conveyed past the guns. In a manual gun operation,typically the object is suspended or otherwise positioned near a spraygun and the operator controls when the gun starts and stops spraying. Apowder spray gun may be selected from a wide variety of gun designs.Since a spraying operation is intended to coat an object evenly, acommon technique for spraying powder is to apply an electrostatic chargeto the powder particles which causes the powder to better adhere to theobject and also results in a more uniform application. Electrostaticspray guns include corona guns and tribocharging guns. In a corona typespray gun, a high voltage electrode is positioned in or near the powderflow path, either within the gun itself or just outside the gun near orat the gun nozzle. In a tribocharging type gun, the powder flow paththrough the gun body is made of suitable materials that impart anelectrostatic charge to the powder as it is forced through the gun body.

The object being sprayed is electrically grounded such that the chargedpowder is attracted to and adheres to the object. This electrostaticattraction increases the transfer efficiency by increasing the amount ofpowder that adheres to the object. Transfer efficiency refers to therelationship between the amount of powder that adheres to the objectbeing sprayed versus the amount of powder sprayed from the gun.

In most electrostatic spray systems, the powder is ejected from the gunnozzle as a cloud. This permits the powder spray to envelope the objectto coat all the surfaces of the object, even when the object isirregular in geometric shape. Multiple guns may be positioned ondifferent sides of the object and/or directed at different angles toincrease the uniformity of the powder applied thereto. However, due tothe inherent nature of the powder spray pattern, there is a substantialamount of powder that does not adhere to the object and ends up eitherfalling to the floor or collecting on other objects and structures inthe immediate area. This non-adherent powder residue is generallyreferred to as powder overspray.

Known powder spray systems utilize a source of powder that feeds powderto the spray guns. The supply system is commonly referred to as a powderfeed center and may include a number of powder pumps that transferpowder from a feed hopper through a series of power hoses to the sprayguns inside the spray booth. In general, an “application system”includes, as the powder flow path, at least spray gun, a powder sourcesuch as a feed hopper, a powder pump and a powder feed hose thatconnects the pump to the gun. In a known feed center, a suction tube orlance extends down into the feed hopper at one end and is connected to apowder pump at an opposite end. The pump draws powder from the hopperand the powder then flows from the pump through the powder feed hose tothe spray gun. In such known systems, the powder flow path typicallyincludes one or more turns, of about ninety degrees or so for example,and these non-straight paths can inhibit thorough cleaning during acolor change operation. The known feed centers also require substantialtime to purge and clean as part of a color change operation.

The presence of powder overspray necessarily dictates that there must bemore powder passing through the spray system than is actually used tocoat the target object. In other words, a substantial amount of powderis cycled through a spray system in the form powder that collects in thebooth and in various filter and collection systems, and this amount ofpowder is far greater than the actual amount of powder that adheres to atarget object. This excess powder is subject to contamination and ingeneral adds to the problem of purging and cleaning the spray system inpreparation for a color changeover.

Because powder overspray is generated during each spraying operation,spraying operations typically are performed within a spray booth. Thespray booth is used for powder containment and may only be partiallyenclosed. Most spray booths have an air flow system that contains thepowder overspray within the structure of the booth by producing anegative pressure zone that draws air from the powder booth along withpowder overspray that is entrained in the air flow. The powder laden airis then transferred to a cartridge filter system or cyclone separatorsystem outside the spray booth to recover the powder. However, in knownspray booth systems, the powder overspray still tends to collect on thebooth walls, ceiling and the booth floor. In electrostatic systemsespecially, the powder overspray will also tend to be attracted to andcollect on any structure that is electrically grounded. The powderparticles tend to be very small and well dispersed and therefore cancollect in the smallest of recesses, seams and crevices and irregularspray booth wall structures.

Powder overspray presents a two-fold challenge. First, if possible it isusually desirable to try to reclaim or recover powder overspray so thatthe powder can be re-used during subsequent spraying operations. Knownpowder recovery systems typically work on the basis of a large airvolume that entrains the powder overspray. These air flow volumes areroutinely generated by conventional high volume exhaust fans. The powderladen air is then filtered, such as for example using cartridge type airfilters or cyclone separators. The separated powder is then sieved toremove impurities and returned to a hopper or powder feed center whereit is supplied once again to the spray guns. In known systems, theactual reintroduction of recovered powder to the powder sprayapplication system is usually accomplished by a positive air pressureconveyance system back to a powder feed center through a series ofhoses, valves and pumps. These additional components significantlyincrease the complexity of cleaning out the spray system for a colorchangeover.

Besides the challenge of recovering powder overspray for subsequent useor disposal, powder overspray that collects within the spray booth mustbe removed from the booth when changing over the powder coating color.In order to switch from one color to another the guns, booth and powderrecovery system must be as completely purged of the previous coloredpowder as possible to prevent contamination of the subsequent coloredpowder. The operation of changing from one color to another is generallyknown as a “color change” operation and it is an ongoing challenge inthe art to make spraying systems that are “quick color change” meaningthat the goal is to keep reducing the down time when the spraying systemis off line in order to clean the spraying apparatus and system. Thus,the amount of in-process powder, as well as the amount of powderoverspray that remains in the spray booth, have a significant impact onthe amount of time and effort it takes to perform a color changeoperation.

In known systems, a significant problem with cleanability and colorchange is that the powder, once it is sprayed from the guns, is notcontinuously recycled back to the feed center, but rather becomesresident at various stages within the spray system. In some systems forexample, powder overspray may reside within the spray booth until aseparate cleaning operation is performed after spraying is completed.Even in systems in which overspray is collected during a sprayingoperation, substantial amounts of powder can remain in the spray booth.Furthermore in some systems, powder overspray that is removed from thespray booth goes to a cyclone separator and falls into and resides in acyclone bin until it is transferred to the feed center. The cyclone bincan be time consuming to clean. The transferred powder may then passthrough a mini-cyclone in the feed center (because the powder from thecyclone is transferred under positive air pressure to the feed centerand therefore is entrained in an air flow) before being dumped back intothe feed hopper. Again, in this stage the powder may still reside in themini-cyclone or sieve for a time before being returned to the feedhopper. If a cartridge filter system is used instead of a cycloneseparator, the powder resides in the filters themselves until pulsecleaning is applied, and in any case the cartridge filters must becompletely replaced during a color changeover.

Cyclones used in powder overspray recovery systems tend to be verylarge, particularly in terms of height. In some manufacturing plants,ceiling height may be limited or the customer may simply not want such ahigh structure for the cyclones. In such cases, shorter cyclones may beused. However, cyclone efficiency is related in part to the aspect ratioof the cyclone, namely the height to diameter ratio. The lower theaspect ratio the less efficient the cyclone for a given exhaust.However, some customers are willing to sacrifice efficiency for asmaller cyclone installation. This applies to single, twin or multiplecyclone arrangements preferably with single yield extractionconfigurations.

A problem with the powder overspray residing in various stages of thespray system is that the powder will tend to find even the smallest nookand cranny and even cake up, and substantial time will need to be spentcleaning this powder out.

Thus, color changeover typically includes having to clean powder fromthree major subsystems: the spray booth, the powder separator, and thefeed center. Each subsystem has its own unique challenges to reducingthe time it takes to completely clean out one powder color to preparethe system for spraying another color. During the cleaning time thespray system is completely down or off-line which represents lost timeand increased costs, in addition to the costs associated with the laborneeded to clean the various system components.

Cleaning a powder coating spray booth can be a labor-intensive effort.Powder coating materials, in varying degrees, tend to coat all theinternal surfaces of the spray booth during a powder coating sprayoperation, which directly impacts color change time. In a productionpowder coating environment, minimizing the system down time to changefrom one color of powder coating material to another is a criticalelement in controlling operational costs. Seams between booth panels andrecessed ledges, such as where access doors or automatic or manual sprayapplication devices may be located, are typically hard to clean areasand tend to hold concentrations of oversprayed powder coating materialthat could present a contamination risk after a color change. Inaddition to seams and ledges and other recesses within the booth,charged powder can adhere to booth interior surfaces.

In typical powder coating booth construction, an outer steel frameworkis provided for supporting individual panel members which form the roof,side and end walls of the booth. These panel members are known to bemade of a fabricated or thermoformed plastic, such as polypropylene,polyvinyl chloride (PVC), polyvinyl carbonate or polycarbonate. Thefloor may also be of thermoformed plastic or stainless steelconstruction. In other known embodiments, powder coating spray boothscan have metallic walls, ceilings and vestibule ends, as well a metallicfloor and exterior support framework.

U.S. Pat. No. 5,833,751 to Tucker is an example of a powder coatingspray booth intended to reduce powder particle adhesion to the interiorsurfaces of the booth during an electrostatic powder spray operation.Tucker discloses a booth chamber comprising a pair of thermoformedplastic shells with smooth curvilinear interior surfaces that areintended to inhibit oversprayed powder particle adhesion. Two identicalends connect with the shells and an external support frame is disclosed,but not shown. Possible booth materials disclosed include polycarbonate.

Known booth materials are available in limited sizes requiring somemethod of seaming to generate the overall size. These seams require mucheffort and cost to achieve a virtually uninterrupted, seamless surface.

In addition, known powder coating spray booths have numerous featuresthat reduce operational efficiencies. These sub-optimal features areevidenced during powder coating color changes between successive runs ofdifferent coating colors and during assembly and maintenance of thebooth itself. Known powder coating spray booths use metallic externalsupport frames and stainless steel or thermoplastic, floors, walls andceilings. During an electrostatic powder spray coating operation,oversprayed powder material can actually be attracted and adhere tothese booth interior surfaces. Higher concentrations of oversprayedpowder coating material are typically seen in the immediate vicinity ofthe highly conductive steel frame members, which are typically grounded.Although thermoformed plastics are typically thought of as insulators,their insulation properties vary and powder particle adhesion can varywith the conductance and resistance of these materials. With age,physical properties of the thermoformed plastic materials can changewith corresponding increases in powder particle adhesion, as they canabsorb moisture from the ambient air over time. Ultraviolet light isalso known to change the physical properties of thermoplastics overtime.

In addition, typical booths have numerous design features that act toincrease accumulated oversprayed powder coating materials in the spraybooth, thus increasing cleaning times during color change operations. Inbooths using panel members connected with each other and supported by anexternal frame, numerous seams exist throughout the booth interior thatentrap oversprayed powder coating material, thereby making the boothharder to clean during a color change or routine booth maintenance. Inaddition to the seams, ledges are present in some powder coating spraybooths on which spray gun application devices rest and are mounted, andwhere openings for doors and other access portals are reinforced andsecured, for example. These ledges can either extend into the booth or,more typically, extend away from the inner surface of the booth. Even ifotherwise angled or curved toward the floor from the typically verticalside walls, oversprayed powder coating material still tends toaccumulate in these areas, thus making them more difficult to clean, aswell.

Known prior systems for removing powder overspray from a spray boothinclude active systems in which floor sweepers and other mechanicaldevices are used to mechanically contact the powder and push it off thefloor into a receiving device. These systems however tend to becumbersome and are not thorough in the amount of powder removed from thebooth. A substantial effort by one or more operators is still requiredto completely remove powder from the booth. Thus there can be a largeamount of in-process powder and powder overspray on the booth structure.

In passive removal systems, powder is removed from the floor in anon-contact manner. In one known system, a rectangular floor in the formof a continuous linearly moving belt transports powder over to acollection device such as a vacuum system that removes powder from thebelt. Such systems are very complicated mechanically and do not do anadequate job in removing powder from the belt, so much so that in somecases a color change requires a change of the belt itself.

It is desired therefore to provide a spray booth that is easy to cleanas part of a color change operation and operates so as to minimize theamount of in-process powder and the amount of powder overspray remainingin the spray booth after a spraying operation is completed.

It is further desired to provide a powder coating spray system andassociated subsystems including a powder recovery system thatsubstantially reduce the residence time of powder overspray within thesystem between the spray gun nozzle and the feed hopper. The spraysystem should remove as much powder overspray as possible from the spraybooth and transfer it back to the feed center during a sprayingoperation. Thus the amount of residual powder overspray needing to bemanually cleaned from the subsystems will be largely eliminated. It isfurther desired to provide a powder feed center that is easier andfaster to clean as part of a color change operation.

It is further desired to provide method and apparatus for influencingthe efficiency of a cyclone separator used with a powder coatingspraying system.

SUMMARY OF THE PRESENT INVENTION

The present invention is directed to a new powder coating spray systemthat is dramatically faster and easier to clean, thereby significantlyreducing the time required for a color changeover. In accordance withone aspect of the invention, a powder coating spray system produces aregion of high air flow through a spray booth to extract powderoverspray from the booth. The high air flow is produced by a lowpressure source outside the booth. In one embodiment, a suction duct ispositioned above the booth floor and the air flow into and through theduct sucks up powder from the floor and transports it outside the boothto a collection device. Relative rotation between the floor and the ductpermits the entire floor to be swept, and in one embodiment the booth isgenerally cylindrical and the floor is round rotates about alongitudinal axis of the booth. In another embodiment of the invention,the spray booth walls and floor are made of non-conductive compositematerials.

In accordance with another aspect of the invention, powder overspraythat is extracted from a spray booth is recovered back to a powdersupply that is used to supply powder to the spray guns inside the spraybooth. In one embodiment, the extracted powder overspray is separatedfrom the high flow air stream by a cyclone separator. The powder fallsinto a transfer pan and a vacuum is used to convey the powder from thetransfer pan to a vacuum receiver. The powder is then discharged to thefeed hopper in the feed center. The use of a vacuum to convey powderfrom the cyclone to the feed center in effect permits substantially allof the powder overspray to be recovered from the spray booth directly tothe feed hopper with minimal dwell or residence time within the cycloneor vacuum receiver subsystems during a spraying operation. What littlepowder remains from the powder recovery during spraying operations canbe quickly and easily blown-off as part of a cleaning and colorchangeover procedure.

In accordance with another aspect of the invention, cyclone efficiencymay be influenced and improved by applying a negative pressure at anoutlet of the cyclone to convey powder to a container. In oneembodiment, the container may be the feed hopper to support theapplication process. In one embodiment, a vacuum pump is coupled to thecyclone outlet. The vacuum pump produces an induced air volume thatentrains powder from the cyclone outlet and conveys the entrained powderto the container. The coupling from the vacuum source to the cycloneoutlet is air tight during recovery and conveyance. In accordance withanother aspect of the invention, cyclone efficiency is influenced bymaintaining a predetermined relationship between the static pressure ofthe cyclone and the induced air volume of the vacuum source. This allowsfor the negative pressure to entrain the powder located at the cycloneyield outlet and recover additional powder at the container that wouldotherwise be lost through the cyclone exhaust (sometimes referred to inthe art as the tailings exhaust).

In accordance with another aspect of the invention, cleaning of thesystem is facilitated by a powder vacuum receiver in the powder feedcenter that can be rotated for easy powder blow-off, and that has agravity controlled outlet door that periodically discharges recoveredpowder to the feed hopper. In one embodiment the receiver uses colorspecific filters that are easily replaced during a color changeover.

In accordance with another aspect of the invention, the powder feedcenter is designed to facilitate faster color change operations. In oneembodiment, one or more powder pumps are used that have an in-linepowder flow path that extends between the pump powder inlet from thesuction tube to the pump powder outlet that is connected with the spraygun feed hose. This arrangement provides a straight through powder flowpath without any ninety degree turns. In a further embodiment, a powderspray gun is used that also provides a straight through powder flowpath. Thus, a powder application system is provided in which powderflows from the feed hopper to the spray gun nozzle along a smooth,continuous flow path without any sharp or severe bends in the flow path.When used in combination with a powder recovery system of the presentinvention, an application system is provided that is easy and fast toclean and perform a color change operation, since less in process powderis used, the overspray is substantially continuously returned to thefeed center, and easy to clean/purge powder flow paths are provided.

In accordance with another aspect of the invention, a color changeoverprocedure is provided that substantially reduces system down time. Inone embodiment, the spray booth and recovery system are cleaned duringthe same time period to significantly reduce color changeover time. In aspecific embodiment of the spray booth, the rotatable floor can also beaxially position into a sealed relationship with the booth walls. Thespray guns are blown-off by air jets disposed near gun slots in thebooth wall as the guns are retracted from the spray booth. The powderpumps, feed hoses and spray guns are then purged into the sealed spraybooth. The sealed floor permits an operator to blow-off powder from thebooth walls, ceiling and the extraction duct. Once the spray booth hasbeen blown down, the floor is lowered and the extraction system operatedto extract any remaining powder from the booth floor and seal to anafter-filter system or waste.

In another embodiment, the vacuum line from the cyclone to the vacuumreceiver is cleaned by drawing cleaning elements through the vacuum lineinto the receiver. In one version, the cleaning elements are oversizefoam cylinders that wipe the vacuum line as they travel therethrough. Inthis embodiment, the vacuum receiver is blown off when rotated to ahorizontal position and the color specific filters replaced. Other partsof the feed center are also cleaned at this time.

In another embodiment of the invention, a powder coating spray systemwith powder overspray recovery during a spraying operation includes agenerally cylindrical spray booth with a rotatable floor that rotatesunder a powder extraction duct suspended just above the floor. Powderoverspray on the floor is drawn up into the duct while the floor rotatesthereunder. The extracted powder overspray laden air is then drawn intoa cyclone separator, and a vacuum pump/receiver unit in the feed centeris used to convey powder from the cyclone via a vacuum line to thevacuum receiver. The vacuum receiver accumulates the recovered powderand periodically opens and discharges the recovered powder to a feedhopper via a sieve. The receiver filter is reverse shock pulsed duringthe discharge cycle to knock powder off the filter. Use of the powderextraction device and rotating floor, in combination with the vacuumtransfer from the cyclone to the feed center, results in very smallquantities of powder overspray remaining in the spray system components,thus minimizing cleaning required for color changeover.

In accordance with another embodiment of the invention, a powderoverspray recovery system uses a negative pressure high air flow toproduce a suction within a spray booth to extract powder overspray to afirst collection device during a spraying operation. A vacuum receiverin a powder feed center is used to transfer the powder overspray fromthe first collection device to the feed hopper in the feed center. Thusthe overspray powder is substantially maintained in a continuoustransfer from the time it is sprayed from a spray gun until it returnsto the feed hopper for re-use. The vacuum transfer significantlysimplifies the powder clean process needed prior to a color changeover.The recovery system leaves a minimal amount of powder in the systemcomponents during a spraying operation so that clean-up time issubstantially reduced, thus making for a very fast color changeoveroperation.

The present invention is also directed to improved spray booth designsthat are particularly suited for electrostatic spraying operations,although the various aspects of the invention may be incorporated intospray booths that do not utilize electrostatic spraying apparatus.According to one aspect of the invention, a powder extraction system iscontemplated in which powder overspray can be continuously extractedfrom the booth even during a spraying operation. In one embodiment ofthe invention, a powder spray booth includes a booth canopy wall andceiling arrangement to contain powder during a spraying operation; and abooth floor that is rotatable relative to the booth wall during aspraying operation. The booth may be generally cylindrical in shape witha round floor. The floor can be rotated about a vertical axis that isalso the longitudinal axis of the spray booth. The booth canopy andceiling are supported on a base frame separately from the floor. By thisarrangement, the floor can be rotated relative to the booth canopy. Bycontinuously removing powder overspray in a real-time manner during apowder spraying operation, the amount of in-process powder issubstantially reduced and the time and effort required to clean thebooth as part of a color changeover is dramatically and significantlyreduced.

In accordance with another aspect of the invention, a powder extractionmechanism is provided for removing powder overspray from the boothfloor. In one embodiment, the extraction mechanism is a duct thatextends across the booth floor and supported just off the floor. Anegative pressure source is connected to the duct to cause a suctioneffect by which powder overspray is removed from the floor andtransported via the extraction duct to a collection device that isdisposed outside the booth. In a preferred form, the extractionmechanism is stationary with respect to the rotating floor and extendsdiametrically across the floor.

In accordance with another aspect of the invention, the booth floor canbe translated as well as rotated. In one embodiment, the booth floor canbe axially translated along the axis of rotation. The floor can be movedto a first axial position in which the floor is free to rotate during aspraying operation, and a second axial position where the floorsealingly contacts the bottom of the booth canopy or wall during a colorchange operation. A source of pressurized air is positioned to blowpowder from the seal as part of a color change operation.

Still a further aspect of the invention concerns a mechanism foreffecting the axial translation of the floor. In one embodiment thefloor is moved by a floor lifter mechanism that moves the floor betweenthe first and second axial positions. In one embodiment the liftermechanism is a pneumatic actuator that acts on a rocker arm to raise andlower the booth floor.

In accordance with another aspect of the invention, a cyclone system isused to separate the powder overspray from the air drawn in by theextraction duct. A fan is connected to the cyclone system which in turnis connected to the extraction duct. The air flow that is pulled throughthe duct creates a negative air pressure flow that draws up powder thathas collected on the booth floor into the extraction duct and alsoprovides containment air flow within the booth canopy. In oneembodiment, the cyclone system is provided with a by-pass valve forselecting between powder overspray reclaim and non-reclaim operatingmodes.

Still a further aspect of the invention relates to the use of compositematerials for the spray booth and floor that are very low inconductivity to minimize powder adhering to the booth and floor, whilepossessing significant structural properties that enable theconfiguration to be mechanically sound. In one embodiment, the boothcanopy is made of two composite half cylinders that are entirelyself-supporting so that the canopy and ceiling can be suspended over anunderlying rotatable floor. In this embodiment the floor is also made ofvery low conductivity composite materials with sufficient structuralstrength to permit a floor design whereby the floor can be rotated on acentral hub.

These and other aspects and advantages of the invention will be readilyappreciated by those skilled in the art from the following detaileddescription of exemplary embodiments of the invention with reference tothe accompanying Figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1 and 1A are isometric schematic representations of a powderspraying system in accordance with the invention, with FIG. 1Aillustrating a manual spray booth or vestibule attached to the mainspray booth;

FIG. 2 is a simplified top view of the spray booth and cyclone system;

FIGS. 3 and 4 illustrate in elevation a typical powder coating systemlayout;

FIG. 5 is a plan view of a frame that supports a spray booth of thepresent invention;

FIGS. 6 and 7 illustrate detail of a floor lift assembly for the spraybooth, with the floor in the up and down positions respectively;

FIG. 8 is a plan view of the spray booth floor;

FIG. 9 is a cross-section of the floor taken along the line 9A-9A inFIG. 8;

FIG. 10 is an embodiment of a floor hub assembly in plan;

FIG. 11 is the hub assembly of FIG. 10 in vertical cross-section alongthe line 11-11 in FIG. 10;

FIGS. 12 and 12A is an extraction duct shown in elevation andperspective respectively;

FIG. 13 is the extraction duct of FIG. 12 shown in plan;

FIG. 14 is a cross-section of the extraction duct of FIG. 12 along theline 13-13 in FIG. 12;

FIGS. 15A and 15B illustrate an alternative embodiment of an extractionduct, illustrated in exploded perspective in FIG. 15A and in perspectiveas assembled in FIG. 15B;

FIG. 16 is the extraction duct of FIG. 15 shown in lateralcross-section;

FIG. 16A is an alternative embodiment of the extraction duct of FIGS.15A and 16 shown in lateral cross-section;

FIG. 17 is an alternative embodiment of a canopy support arrangement;

FIG. 18 is a bottom view of a bypass plenum;

FIGS. 19A and 19B illustrate in elevation the bypass plenum of FIG. 18with a bypass valve and actuator arrangement shown in two positionscorresponding to a reclaim and non-reclaim mode;

FIG. 20 illustrates an embodiment of the valve element of FIG. 19 infront elevation; and

FIG. 21 is a cross-section of the valve element of FIG. 20 taken alongthe line 21-21;

FIG. 22 is a simplified functional schematic of an embodiment of apowder overspray recovery system according to the invention;

FIG. 23 is an elevation of a cyclone system in accordance with theinvention;

FIGS. 24 and 25 are plan and elevation views respectively of a cyclonevacuum interface device in accordance with the invention;

FIG. 25A is an end view of the vacuum interface device of FIGS. 24 and25;

FIG. 26 is an exploded elevation of a vacuum receiver unit in accordancewith the invention;

FIG. 27 is a side elevation of the vacuum receiver of FIG. 26 taken at a90 degree rotation;

FIG. 28 is a side elevation of the vacuum receiver unit of FIG. 26 in anassembled condition;

FIG. 29 illustrates part of a powder feed center in elevation inaccordance with the invention;

FIG. 30 is a partial front elevation of the feed center with the feedhopper removed;

FIG. 31 is one embodiment of a powder pump illustrated in longitudinalcross-section;

FIG. 32 is an enlarged view of the purge manifold arrangement of FIG.30;

FIGS. 33 and 34 are schematic illustrations of exemplary powder coatingapplication systems using an in-line powder pump and spray gun;

FIG. 35 is a representative graph comparing spray patterncharacteristics between application systems using a conventional powderpump and an in-line powder pump of the present invention; and

FIG. 36 is a schematic illustration of an application system using analternative embodiment of the in-line pump arrangement of FIG. 33.

DETAILED DESCRIPTION OF THE INVENTION

Introduction

By way of introduction, the present invention is directed to providing apowder recovery system that takes most of the powder overspray producedin a powder spray booth during a spraying operation and returns it on areal-time basis to the powder feed center. In one embodiment, a powderscavenging protocol is used to recover powder overspray from the spraybooth on a continuous basis and return the scavenged powder to theapplication system on a nearly continuous basis. The powder overspray isalso preferably removed from a cyclone separator and returned to thefeed center on a continuous basis. By “scavenging” is simply meant thecollection and transfer of powder from the time the powder is sprayed bya gun until the powder is returned to the feed center.

As used herein, the terms “powder recovery” and “powder collection” areused interchangeably. By effectively and continuously recovering most ofthe powder overspray, cleanup is greatly simplified therebysubstantially reducing color changeover time as compared to priorsystems. One embodiment of the recovery system in general includes apowder extraction system associated with the spray booth, a first powdercollection/separation system, and a vacuum conveyance system in the feedcenter. Vacuum “convey” and “transfer” are also used interchangeablyherein. It is important to note that although a complete recovery systemis provided, various subsystem features may be used singly or incombination with other features disclosed herein. For example, thevacuum transfer system may be used with any powder spray booth powderextraction system, and also is not necessarily dependent on the designof the first collection/separation system. Exemplary embodimentsincluding exemplary alternative embodiments are described here, however,such descriptions are not intended to be and should not be construed tobe an exhaustive list. Those skilled in the art will readily understandthat many alternatives are available for the specific embodimentsdescribed herein.

In addition to powder recovery during a spraying operation, the powderrecovery system reduces the amount of residue powder in the spray systemto such an extent that color changeover time is substantially reduced.Thus, the present invention also contemplates a color change procedurethat is enhanced by various aspects of the recovery system itself. Thecolor changeover procedure however may also be realized with alternativeembodiments of the powder recovery system and is therefore not limitedto being implemented by the exemplary embodiments of the recovery systemdescribed herein.

For ease of explanation, the various subsystems will be describedherein, followed by a detailed description of the color changeoverprocedure.

With reference to the drawings, the present invention is directed to apowder coating spray system and a powder overspray recovery system and acolor changeover procedure, as well as specific components within such asystem, to improve the cleanability and reduce the time to effect colorchange operations, while at the same time minimizing impact on transferefficiency while maximizing impact on containment and recovery of thepowder overspray. Various aspects of the invention are described hereinin an exemplary manner, and as part of an overall spraying system, butsuch descriptions are not to be construed in a limiting sense. Thevarious aspects of the invention may be used individually or in anyvarious combinations as required for a particular application.Furthermore, although the present invention is described with respect tothe use of electrostatic spray technology, the invention is not limitedto the use of electrostatic spraying apparatus.

Powder Coating Spray System and Powder Spray Booth

FIG. 1 illustrates a powder coating spraying system 1 with several ofthe main components illustrated in a schematic fashion for ease ofillustration. Such components are generally referenced with lettersrather than numbers, and are well known and need not be described indetail. Accordingly, the present invention is described in detail as tothose elements that relate to the various aspects of the invention.

The system 1 generally includes a spray booth 10. Note in FIG. 1 thatthe spray booth 10 is represented in a “transparent” manner so that thebasic arrangement of components within the booth 10 can be illustrated.In actual practice the booth 10 is made of non-conductive compositematerials that are not necessarily transparent, although there is nospecific limitation on the choice of materials used for the booth 10. Ina preferred but not necessarily required embodiment of the spray booth10, the booth is constructed from of materials that are very low inconductivity and are composite in nature. These materials render thebooth 10 substantially self-supporting and seamless. A suitablemanufacturing process and structure for the booth 10 out of suchcomposite materials is fully described in co-pending U.S. patentapplication Ser. No. 09/550,353 filed on Apr. 14, 2000 for POWDERCOATING BOOTH CONTAINMENT STRUCTURE, and also described in co-pendingPCT Application No. PCT/US 01/40524 filed on Apr. 14, 2001 for POWDERCOATING BOOTH CONTAINMENT STRUCTURE, which applications are owned incommon by the assignee of the present invention, the entire disclosuresof which are fully incorporated herein by reference. Although thesestructure and materials for the booth 10 are preferred for electrostaticapplications, the present invention is not limited to the use of a boothwith such structural and materials characteristics, particularly insystems that will not utilize electrostatic spraying devices.

In the illustrated embodiment, the booth 10 is generally cylindrical inshape, including a vertically extending canopy or wall structure 12, aceiling, cover or top 14 and a floor 16. In this example, the canopy 12is realized in the form of two generally hemispherical halves that arejoined together by mating flanges (not shown). The halves can be joinedby non-conductive fasteners or adhesive so that the basic cylindricalshell is non-conductive. It is preferred although not necessary that theceiling 14 and the floor 16 also be seamless and made from the samenon-conductive composite materials as the canopy. The above-cited patentapplication discloses a composite booth structure with sufficientstrength to permit humans to walk on the floor 16. The canopy 12 is alsoself-supporting such that no exterior frame is needed to support thebooth 10. The canopy 12 and the ceiling 14 may be integrally formed ifso desired.

Although the booth 10 is generally cylindrical in shape, it is not afully enclosed structure. Access doors and other openings are providedto facilitate a spraying operation. For example, a plurality of gunslots 18 are provided on opposite sides of the booth 10 to permit acorresponding plurality of spray guns 20 to extend into and be withdrawnfrom the spray booth 10. The guns 20 may be of any suitable design,including a gun design as disclosed in co-pending U.S. patentapplication Ser. No. 09/667,663 filed on Sep. 22, 2000 for POWDER SPRAYGUN, the entire disclosure of which is fully incorporated herein byreference.

For clarity and ease of illustration, the spray guns 20 are onlyillustrated on one side of the booth 10 in FIGS. 1 and 1A, it beingunderstood that second set of spray guns and a gun mover may be used onthe opposite of the booth 10. The particular system 1 illustrated inFIG. 1 is an automatic system in which the spray guns 20 are mounted ona suitable support frame 22 that is installed on a gun mover 24. The gunmover 24 and the frame 22 are illustrated schematically since any of anumber of gun mover and support designs may be used. In this example,the gun mover 24 includes an oscillator 26 that can raise and lower thespray guns 20 along the gun slots 18.

The spray booth 10 however may also be used for manual sprayingoperations, and therefore may be equipped with an optional vestibuleassembly 28 (FIG. 1A only). Preferably the vestibule 28 is made of thesame composite materials and structure as the canopy 12.

Continuing with the general description of the system 1, the booth 10 issupported off the shop floor F by a support frame or base 30. The base30 is supported on the floor F by a pair of parallel rigid bars 32 (onlyone shown in FIG. 1) which are described in greater detail hereinafter.In accordance with one aspect of the invention, the booth 10 is fullysupported on the frame 30 just off the shop floor F such that the entirebooth/frame 10/30 assembly can be installed as a retrofit for apreexisting spray booth without the need to modify elevation of the shopfloor F or part conveyor height. Thus there is no need to trench orlower the floor F to accommodate any portion of the spray booth 10 orframe 30. In the illustrated embodiment herein, for example, the boothfloor 16 is installed a mere 12 inches or so above the shop floor F.This permits simple ductwork to be used to interconnect the variousconventional components of the spraying system 1.

The upper portion of the canopy 12 and the ceiling 14 are provided witha conveyor slot 34 that extends diametrically across the entire booth10. Objects that are to be sprayed are suspended (not shown) from theconveyor C (FIG. 2) in a conventional manner so that the objects can bepassed into and through the booth 10 past the spray guns 20.

An extraction duct 40 is installed in the booth 10 in close proximity tothe floor 16. This extraction duct 40 has a discharge end is in fluidcommunication with a dual or twin cyclone separator system 42. Inaccordance with one aspect of the invention, a substantial negativepressure is produced in the extraction duct 40 via air drawn byoperation of the cyclone system 42 and an after-filter system assembly60 (FIG. 4). A large blower in the after-filter system 60 produces asubstantial air flow from the booth 10 interior into the extraction duct40 in the nature of a vacuuming effect such that powder overspray on thefloor 16 is drawn up into the duct 40 and entrained in the air flowtherein. This powder laden air is drawn into the cyclone system 42 viaappropriate ductwork 44 that connects through an opening in the canopy12 to the discharge end of the extraction duct 40. The opposite end ofthe extraction duct 40 terminates at an access door duct (172). Thecyclone system 42 exhaust air passes to the secondary after-filtersystem (60) or collection system (not shown in FIG. 1) for removal offines. A dual cyclone arrangement 42 a,b is preferably but notnecessarily used in order to provide a substantial air flow through theextraction duct 40 to remove powder overspray from the floor 12.

In general, the present invention is described herein with reference toan embodiment in which powder overspray is removed from the booth 10 andfed to a powder collection system. In the described embodiments, thepowder collection system includes either a powder reclaim system throughoperation of a cyclone system and apparatus for conveying powder fromthe cyclone back to the feed center. Alternatively, in the presentapplication we describe a powder collection system in which the powderis not reclaimed but rather is diverted past the cyclone system directlyto an after-filter or other arrangement for the powder to be disposed.The present invention therefore does not depend on the particular powdercollection system used outside but rather is directed to extractingpowder overspray from within the spray booth, and the term “powdercollection” should be construed in its broadest sense to encompass anypost-spraying disposition of the powder overspray outside the booth,whether the powder overspray is reclaimed or not.

In FIG. 1 the cyclone system 42 is illustrated as being supported on theshop floor F by a cyclone support frame 43. Alternatively, the cyclonesystem 42 may be supported directly on the booth support frame 30.

The air flow that is drawn through the extraction duct 40 also providesa containment air flow within the booth 10 interior. Substantial volumeof air is drawn into the booth 10 via various openings and access doorsprovided in the canopy 12.

The extraction duct 40 is supported at each end by the base 30, not thebooth floor 16. The canopy 12 and installed ceiling 14 are alsosupported by the base 30 and not the booth floor 16. In accordance withanother aspect of the invention, the booth floor 16 is rotatable aboutthe central longitudinal axis X of the booth 10. The extraction duct 40in this case is stationary relative to the rotating floor 16 so as toprovide a sweeping action between the extraction duct 40 and the floor16 surface. In this manner, the floor is cleaned of powder overspray asit collects on the floor even during a spraying operation. Of particularnote is that the overspray may be extracted during or after a sprayingoperation.

Completing the general description of the system 1, the cyclone system42 may be conventional in design and separates the entrained powder fromthe drawn air. The system 1 also includes a powder feed center 46 thatsupplies powder to the spray guns 20 through an appropriate system of afeed hopper, feed hoses and powder pumps, as is well known to thoseskilled in the art. A control console or system 48 is also provided thatcontrols the operation of the guns 20, the cyclone system 42, the gunmovers 26, the conveyor C, floor 16 rotation and position, and the feedcenter 48. The control system 48 may be conventional in design. Suitablecontrol systems are described in U.S. Pat. Nos. 5,454,256 and 5,718,767;a suitable cyclone system is disclosed in U.S. Pat. No. 5,788,728; and asuitable feed center is disclosed in U.S. provisional patent applicationSer. No. 60/154,624 which corresponds to copending PCT applicationnumber 00/25383 filed on Sep. 15, 2000 for QUICK COLOR CHANGE POWDERCOATING SYSTEM, the entire disclosures all of which are fullyincorporated herein by reference. Powder that is separated by thecyclone system 42 may be returned to the feed center 46 for reuse (notshown in FIG. 1).

In accordance with another aspect of the invention, the floor 16 notonly can rotate, but also can be axially translated along the axis ofrotation X. This permits the floor 16 to have at least two axialpositions, the first being a lowered position in which the floor 16 isfree to rotate during a spray coating operation, and a second positionin which the floor 16 is raised and is sealed against the lower edge ofthe canopy 12 walls during a color change operation. By moving the floor16 into the sealed or raised position, an operator can use an air wandor other suitable device to blow down powder overspray that may havecollected on the canopy 12, the ceiling 14 or the outside of theextraction duct 40, into the extraction duct 40. For example, theextraction duct 40 is preferably at least partly made of metal to act asan ion collector for electrostatic spraying systems. Consequently,powder will adhere and collect on the outer surface of the extractionduct 40, but this small amount of powder can quickly and easily be blownoff and will be quickly swept up into the duct 40. The blower assembly60 preferably remains on at all times during spraying and cleaning/colorchange operations.

In its raised position, the floor 16 is fully supported (as will bedescribed herein) so that one or more operators may walk across thefloor as required for air cleaning the booth 10, usually as part of acolor change operation. The floor 16 is then lowered and rotated whileoperating the cyclone system 42, thereby removing the last remainingquantities of overspray. Color change therefore is a very fast andsimple procedure in terms of cleaning out the spray booth 10. Thepreferred use of the composite materials for the booth 10 substantiallyeliminates powder collecting on the canopy 12 and ceiling 14, andpermits the extraction duct 40 to easily and efficiently remove powderfrom the floor 16. The floor 16 is non-conductive except at the drivehub assembly (not shown in FIG. 1), but the drive hub assembly islocated within the extraction duct 40 such that powder cannot collect atthe hub due to the high air flow through the duct 40.

The outside surfaces of the housings or bodies of the guns 20 may becleaned by air jets 21 (FIG. 4) that are positioned at the gun slots 18.As illustrated in the enlarged portion of FIG. 4, the air jets 21 (onefor each gun body) are installed on a common air tube 21 a that extendsvertically along the length of its associated gun slot 18. In thisembodiment there is an air tube/jet arrangement for each gun slot 18.The air jets 21 blow high pressure air across each gun body as the guns20 are withdrawn from the booth 10 by the gun movers 24, therebycleaning powder from the guns 20 and blowing powder off the gun bodiesinto the booth 10 where it is extracted via the extraction duct 40.

A significant aspect of the system 10 is that it can be realized as partof a retrofit on an existing system without the need for major changesto the shop area. For example, in the illustrated embodiment, the boothfloor 16 is a mere 12 inches above the shop floor F. This permits thebooth 10 to be interconnected if required with preexisting cyclone andfeed systems, as well as fitting under existing conveyor systems.

With reference to FIG. 2, the spray booth 10 is illustrated in asimplified manner from a top or plan view with the base 30 and theceiling 14 omitted. The canopy 12 includes access doors 50 that permitlarger objects to be conveyed into the spray booth 10. As illustrated inFIG. 1, the doors 50 may be similar to a “dutch” door arrangement inwhich there are upper doors 50 a and lower doors 50 b. The lower doors50 b are typically opened simply to permit an operator easy access tothe booth 10 interior. These openings provide the major source of airthat enters the booth 10 during a spraying operation when the cyclonesystem 42 is operating. This primary air flow pattern serves ascontainment air to keep the powder overspray within the booth 10.Although air flow will also be produced in other areas of the booth 10,for example at the conveyor slot 34, these secondary openings and gapscontribute much less to the overall containment air pattern than the airentering through the various door openings and any vestibule whenvestibules are used. The diametric centerline Y of the primary air flowpattern, such as for example through the access doors 50, forms an angleα with the centerline Z of the extraction duct 40. Preferably the angleα is about 45 degrees. Thus the air flow (as indicated by directionalarrows AA) into the booth 10 is not parallel with the extraction airflow into the duct 40. This causes air flowing into the booth 10 to haveto turn and head downward (see also FIG. 4) in order to reach the lowpressure zone near the extraction duct 40 along the floor 16, asrepresented by the directional arrow AA. This air flow pattern thusproduces a descending outer air circulation around the booth 10 thatresults in a relatively low air flow in the central region of the spraybooth 10, which central region is where the spray guns 20 are disposedto spray an object. This relatively calm central region means that thepowder spray patterns are not adversely affected by the rather highvolume of containment air flowing into the booth 10. Thus, excellentpowder containment is effected without a significant effect on thetransfer efficiency of the guns 20.

FIGS. 3 and 4 illustrate in plan a typical floor layout for the system 1(the spray booth 10 is illustrated in vertical cross-section). Note thatin FIG. 4 we illustrate the use of two gun movers 22. In thisarrangement, the cyclone system 42 is connected to the outlet of theextraction duct 40 by a transition elbow duct 52. The powder laden airflows from the extraction duct 40, into the elbow 52 and up the verticalconnecting ductwork 44 to the tangential inlet 54 of the cyclone 42. Thecyclone system 42 includes a bypass plenum 56 that has areclaim/non-reclaim bypass valve therein, which will be describedfurther hereinafter. When the cyclone is in a “reclaim” mode ofoperation, the cyclone exhaust air, which typically still includespowder fines that were not removed by the cyclonic filtering action,passes through additional exhaust ductwork to a conventionalafter-filter assembly 60 (FIG. 4). Powder that is separated by thecyclone 42 falls into a cyclone hopper 62 (FIG. 3) from where it can bemanually removed and returned to the feed center 46 main hopper (notshown) or can be automatically transferred to the feed center 46 bypositive air pressure and appropriate ductwork, valves and filters. Inprior art systems, a pinch valve assembly (not shown) has sometimes beeninstalled below the cyclone hopper 62 to control the transfer of thereclaimed powder from the cyclone 42 to the feed center 46. In thenon-reclaim mode of operation, the cyclone system 42 is in effect takenoff line by operation of the bypass valve, so that the powder laden airfrom the extraction duct 40 passes through the ductwork 44 and straightthrough the plenum 56 to the exhaust duct 58 and from there into theafter-filter assembly 60. Note that the main blower (not shown) forproducing the needed air flow within the booth 10, the extraction duct40, the cyclone system 42 and the interconnecting duct work isphysically located in the after-filter assembly 60. The main blower canbe conveniently located elsewhere in the overall system as required.

FIG. 4 shows schematically some additional detail of a suitable gunmover 24. Note that the view angle of FIG. 4 is rotated from the viewangle of FIG. 3 to show additional details, and that in FIG. 4 thecyclone system 42 has been omitted for clarity. The guns 20 are mountedon a frame or gun mount 22 which typically includes a number of tubelengths arranged horizontally and vertically to allow the guns 20 to bepositioned as required. The oscillator 26 is supported on a moveableplatform 64 that can translate back and forth on a base 66. The platform64 is moved pneumatically or but other suitable means by the controlsystem 48 so as to move the guns 20 horizontally into and out of thebooth 10. The oscillator 26 moves vertically to allow the guns to beraised and lowered during a spraying operation. Preferably but notnecessarily the gun mover bases 66 are supported on wheel assemblies 106(FIG. 6) that allow the gun movers 24 to be rolled across the shop floor(see FIG. 6). This allows the gun movers 24 to be part of an overallmodular spraying system in that various main components can be added onand separately assembled to the booth 10 and frame 30 assembly asrequired.

With reference to FIG. 5, the support frame 30 is realized in the formof a octagonal framework although the actual geometry and configurationmay be selected as required. The inner perimeter configuration of theframe 30 however is circular to accommodate the booth floor 16. Theframe 30 includes a series of interconnected trusses 68 and frame barsor spars 70. A removable skirt or cover 72 is provided for aestheticsand to prevent accidental contact with the rotating floor 16. The frame30 also supports various equipment such as a floor drive motor 74 and aseries of four floor lifters 76. The bottom of the frame 30 rests on twoparallel floor base support bars 32. As shown in greater detail in FIG.6, the support bars 32 have wheels or casters 78 installed on each end.This permits the entire booth 10 and frame assembly 30 to be easilymoved into position on the shop floor F.

The dashed lines W represent where the booth vertical canopy 12 wallsalign with the frame. The circle FL indicates the outer perimeter of thebooth floor 16. Thus it is apparent that the floor 16 diameter isgreater than the diameter of the canopy. In a typical booth, the canopymay be about 10 feet for example in diameter and the floor 16 may beabout 11 feet in diameter. There is no practical restriction on thebooth size however. The floor 16 extension past the canopy 12 wall actsas a fall-out pan so that powder that escapes through the gap betweenthe floor 16 and the canopy 12 will alight on the extension. This amountof powder is typically going to be very small and consist mainly offines and thus will tend to be drawn in by operation of the extractionduct 40, as well as a seal blow-off jet that will be describedhereinafter.

A parallel pair of floor hub supports 82 extend across the innerperimeter of the frame 30. These hub supports are rigidly mounted to theframe 30. As will be further explained hereinafter, the floor 16 ismounted on the supports 82 via a hub assembly 84. Thus, the floor 16 isfully supported on the frame 30 as a unit separate from the canopy 12 topermit rotation and vertical movement of the floor 16 relative to thecanopy 12.

The frame 30 supports a number of floor lifter units 76, which in thisembodiment there are four lifters 76 evenly spaced around the frame 30.The basic function of the lifters 76 is to raise and lower the floor 16vertically relative to the bottom edge of the canopy 12 walls. When thefloor is raised, it is sealed against the bottom edge of the canopy 12.When in the lowered position, the floor 16 is free to rotate about thelongitudinal axis X of the canopy, which is also the translation axisfor the vertical movement of the floor 16.

As noted hereinbefore, the frame 30 also supports the ends of theextraction duct 40, and more specifically in this embodiment thetransition duct to the cyclone system and the access door assembly atthe opposite end. This permits the extraction duct to be supported in aposition that is just above the top surface of the floor 16 when thefloor 16 is rotating. The extraction duct 40 is not shown in FIG. 5.

With reference next to FIGS. 6 and 7, the floor 16 includes a thickermiddle section 16 a and then at its periphery thins down to a rigidflange portion 16 b. Four floor lifter units 76 are evenly spaced aboutthe periphery of the floor 16 (see FIG. 5), and FIGS. 6 and 7 illustratein detail one of the lifters 76, with the other three lifters beingsubstantially the same. Although the lifter 76 design illustrated hereinis a preferred design, those skilled in the art will readily appreciatethat there are many available alternative ways to raise and lower thefloor 16, especially since the displacement is rather short, on theorder of about two inches or less. It is only necessary to lower thefloor 16 from the canopy 12 to provide enough clearance so that thefloor 16 can rotate freely. The smaller the gap between the floor 16 andthe bottom of the canopy 12 wall 12 a, the easier it is to containpowder from alighting beyond the canopy 12 wall periphery.

Each lifter 76 comprises three basic elements, namely a pneumaticactuator 90, a rocker arm 92 and a roller 94. In this embodiment, thepneumatic actuator 90 is realized in the form of a conventional aircushion shock commonly found in pneumatic suspension applications. Theactuator 90 includes an inflatable bladder 96 that is supported by apinned flange 98 on one of the trusses 70 of the frame 30. Pressurizedair is supplied to the bladder 96 via an appropriate fitting and airhose assembly 97. The lower end of the bladder is attached or otherwisedisplaces a flange 100 that is pinned to a first end 92 a of the rockerarm 92. The roller 94 is pinned to the opposite end 92 b of the rockerarm and engages the underside of the floor 16 at the region of the floorflange portion 16 b.

The rocker arm 92 is bent approximately at its middle and pinned at 102to the frame 30 so as to be able to pivot about the axis of the pin 102.The control system 48 may be used to control the air pressure applied tothe bladder 97, or this may be a manual control operation. In eithercase, all four lifters 76 are preferably but not necessarily actuated atabout the same time in order to maintain the floor 16 generally level.When the bladder 96 is inflated by the application of pressurized air,the bladder 96 expands thus pushing down the flange 100 which pushesdown the first end 92 a of the rocker arm 92. This causes the rocker armto pivot in a counterclockwise direction (as viewed from theillustration in FIG. 6). The counterclockwise pivoting action raises theroller 94 thus raising the floor 16. The floor 16 will be raised untilit engages with the lower edge of the canopy wall 12 a. This is theraised and sealed position of the floor 16 as shown in FIG. 6, and thefloor is non-rotating when in the raised position. An elastomeric seal104 or other suitable seal is disposed on the floor 16 and engages thelower end of the canopy 12 a when the floor 16 is raised into sealingengagement with the canopy 12.

At least one air jet nozzle 80 is positioned on the frame 30 at theperimeter of the floor 16 to direct pressurized air at the seal 104 whenthe floor 16 is in its lowered position. This air jet 80 cleans the seal104 of any overspray powder after cleaning activities inside the booth10 are completed in preparation for a color changeover. The air jet 80is not otherwise turned on as it is typically not needed. The nozzle 80is preferably positioned near one end of the extraction duct 40 so as toblow powder from the seal 104 directly into the duct 40. The small airmovement induced by the nozzle 80 will be sufficient to draw powder thathas alighted on the floor 16 extension 16 c outside the canopy 12 wallto be swept into the duct 40.

The circumferential elastomeric floor seal 104 is affixed to the floor16 or carried on the bottom of the canopy 12 and forms an air tight sealbetween the floor 16 and the canopy 12 when the floor is in the raisedposition. Any suitable seal or gasket material may be used for the floorseal 104. This permits an operator to enter the booth 12 when the flooris in its raised position and use an air wand or other mechanism to blowpowder off the canopy walls, ceiling and the extraction duct 40 withoutblowing powder out the booth between the floor 16 and the canopy 12 orhaving powder get trapped between the floor 16 and the canopy 12. Thiscleaning operation will typically be performed as part of a color changeoperation.

When the air pressure in the bladder 96 is relieved, the bladder 96contracts and pulls up the first end 92 a of the rocker arm, thuscausing the rocker arm 92 to pivot clockwise (as viewed in FIG. 6). Thisrotation lowers the roller 94 and the floor 16 lowers under the force ofgravity with the roller 94. The roller 94 lowers until it contacts theframe 30. As will be described herein shortly, the floor 16 is mountedon the hub assembly 84 that not only permits the floor to be rotated butalso allow for this axial displacement of the floor 16 relative to thecanopy 12.

FIG. 6 also illustrates that the gun mover base 66 may be supported onwheel assemblies 106 so that the gun movers 22 may be easily connectedand disconnected from the booth frame 30. A pinned connection 108 may beused to releasably connect the gun mover base 66 to the frame 30.

FIG. 6 illustrates another aspect of the invention. Since the floor 16is rotated during spraying and color change/cleaning operations, thecanopy 12 and the ceiling 14 need to be supported separate from thefloor 16. This is accomplished in the illustrated embodiment by the useof hanging knees 110 that are positioned around the frame 30. Each knee110 includes a lower horizontal flange 112 that is bolted or otherwisesecured to the frame 30. The knee 110 extends up then inward toward thebooth 12. The knee further includes a vertically extending flange 114that may be slightly curved to match the curvature of the canopy 12wall. It is preferred although not required that the knees 110 are madeof non-conductive composite materials, such as in accordance with theprocesses described in the above-referenced patent application. However,the knees 110 may be made from any non-conductive material provided thatthe knees 110 have enough rigidity and strength to support the canopy 12and ceiling 14.

Each knee 110 is bonded to its respective portion of the canopy 12 outerwall surface. Any suitable bonding agent may be used and will bedetermined based on the materials of the knee 110 and the canopy 12. Bythis arrangement, the canopy 12 and ceiling 14 are fully supported justabove the floor 16 (which extends under the canopy 12 wall as in FIG. 5)and there are no conductive bolts or plates or other elements that wouldattract the electrostatically charged powder. The use of the compositematerials for the canopy 12 makes the canopy a fully self-supportedstructure that is cantilevered over the floor 16.

In an alternative embodiment illustrated in FIG. 17, the canopy 12 wallis attached to a plurality of hanging knees 190 by screws 192. In FIG.17 the floor 16 is shown for reference purposes. Note in this embodimentthat the lower end 12 a of the canopy 12 wall is substantially reducedin thickness to provide a mounting flange that is attached to a flangeon the hanging knee 190. Each knee 190 is also bolted to a correspondingsupport truss 70 or other firm structure on the booth support frame 30.FIG. 17 further illustrates the provision of the non-conductive plasticshroud 72 that overlays the frame 30 to keep dust out of the frameinterior and for aesthetic value.

With reference to FIGS. 8 and 9, the floor 16 is a multi-layerconstruction of composite materials. The floor 16 includes an inner hubhole 120 formed by an integral annular hub flange 122. As best shown inFIG. 9, the floor 16 is built up in a step-wise fashion so as to haveits greatest thickness in the middle region of the floor 16. The layersare then step-wise eliminated such that the outer perimeter of the flooris formed by the flange 16 b. With reference to FIGS. 8 and 9, the innerhub flange 122 includes four bolt holes 124 that receive mounting boltsto attach the floor 16 to the hub assembly 84. FIG. 9 further showsschematically the laid-up construction of the composite floor 16 whenthe floor is made in accordance with the processes described in theabove-incorporated patent application. The floor 16 upper or activesurface 126 is a layer of gelcoat while the underside surface 128 is alayer of epoxy barrier. In between these two layers are layers of PVCcoring 130 and bi-directional fabric 132. The resulting floor 16 hasvery high strength and rigidity and very low conductivity, therefore,powder overspray will not easily adhere to the floor upper surface 126.

With reference to FIGS. 10 and 11, the hub assembly 84 is supported bythe parallel hollow bar hub supports 82 which extend across the frame 30(FIG. 5) and are mounted to the frame 30 by bolts or other suitablemeans (not shown). Mounted on each support bar 82 is a gear box supportbracket 140. Each bracket 140 may be attached to its respective supportbar 82 by bolts 142 for example. A gear reducer box 144 is mounted onthe brackets 140 by bolts 146. The gear reducer 144 drives a splineshaft 148 in response to rotation of a drive shaft 150 that is coupledto the gear box 144 by a universal joint 152. The drive shaft 150 isturned by a ¼ horsepower motor 74 that is mounted on the frame 30 asdescribed hereinbefore.

The spline shaft 148 meshes with a track hall spline 154 that has aninner spline for the spline shaft 148 and an outer spline that mesheswith a coupling 156. The coupling 156 is mounted on an aluminum hubplate 158 by a cap 160 that is attached to the coupling 156 by bolts162, and a collar 164 that is attached to the coupling 156 by bolts 166.The floor 16 is mounted on the hub plate by bolts 168 that pass throughthe floor hub flange 122 bolt holes 124 (FIG. 8).

By this arrangement, the motor 74 turns the drive shaft 150 through agear reducer 170, with the drive shaft turning the spline shaft 148through the gear reducer 144 that is mounted on the frame 30 via thesupport bars 82. The spline shaft 148 rotation thus rotates the floor 16via the coupling 156. By use of the spline arrangement between the driveshaft 150 and the hub plate 158, the floor 16 can be axially translatedalong the axis X a limited distance as previously described herein underoperation of the floor lifters 76. The control system 48 may beprogrammed to set or adjust the motor 74 speed and hence the floor 16rotation speed.

With reference to FIGS. 12, 12A, and 13-14, the extraction duct 40 inthis embodiment is a metal duct that is mounted on one end to thecyclone elbow duct 52 and at the other end to an access door duct 172.The cyclone elbow duct 52 and the access door duct 172 are both mountedon the frame 30 and support the extraction duct 40 just off the floor16. For reference, the canopy 12 wall location is shown with dashedlines W in FIGS. 12 and 13, and the floor FL is also represented.

The extraction duct 40 includes a lower skirt 174 that tapers downwardlytowards the floor 16 along the longitudinal axis of the duct 40. Thistaper is defined by an angle β. The extraction duct 40 is supportedabout two inches above the floor 16, and the small optional taper β isused to maintain a constant air flow pattern through the duct 40.Without the taper, the higher negative air pressure closest to thecyclone inlet 52 would cause an uneven flow pattern within the booth.When the floor is in the raised position, there is only a very small orzero gap between the duct 40 and the floor 16 at the cyclone duct 52end, and about two inches at the opposite end. Thus at its maximum whenthe floor 16 is lowered, the opposite end has about a four inch or lessgap between the bottom of the duct 40 and the floor 16.

As best illustrated in FIG. 14, the duct 40 further includes two doors176 a and 176 b that are attached to the skirt 174 by suitable hinges178. The hinges 178 allow the doors 176 a,b to open as illustrated inphantom in FIG. 14 to prevent excessive pressure build-up in the duct40. Pressure can build up inside the duct 40 when the floor 16 is in theraised position during booth cleaning and as part of a color changeoperation. But under normal operating conditions, the doors 176 a,b areclosed and held closed by the negative air pressure within the duct 40.As the floor rotates under the duct 40, powder on the floor 16 is drawnup into the air stream inside the duct 40 and carried out to the cyclonesystem 42.

With reference to FIGS. 15A, 15B and 16, in an alternative embodimentthe extraction duct 180 may be partially made of composite materialssimilar to the materials used for the booth 12. The duct 180 includestwo longitudinal metal rails 182 that extend in parallel across thefloor 16 and that are joined at the top by a cover 184. The roundedcover reduces powder buildup on the duct 180 and therefore is preferablybut not necessarily made of composite very low conductivity materials.In contrast to the embodiment of the all metal duct 40, the cover 184 isa two piece cover 184 a,b with each half hinged at the outerlongitudinal ends thereof. The covers thus lift vertically from thelengthwise center point of the duct 180 when open as illustrated inphantom in FIG. 15B and extend up along the canopy wall. FIG. 16Aillustrates another alternative embodiment in which the composite cover184′ comprises two halves 184 a′ and 184 b′ that are hinged lengthwisein a manner similar to the embodiment of FIG. 14. As in the embodimentof FIGS. 15A and 16, the composite duct cover 184′ may, for example, bemade using the processes for making the composite booth 12.

The duct 180 is mounted above the floor 16 and may be installed in amanner similar to the all metal duct 40 embodiment. In accordance withanother aspect of the invention, in some applications it may be requiredto apply additional force to the powder residue that adheres to thefloor 16 if the suction from the duct is insufficient to thoroughlydislodge the powder. In the embodiment of FIGS. 15 and 16, the compositeduct 180 may be formed with internal air passageways 186 within therails 182 through which pressurized air is supplied (not shown). Eachrail 182 is arcuate in shape so as to include an end portion 182 a thatlies on a tangent T that forms an included angle θ with the floor 12.The angle θ is preferably less than ninety degrees.

A series of air jets or orifices 188 are formed in the bottom of eachrail 182 and are in fluid communication via passageways 188 a with theair passageways 186 such that pressurized air is directed out of eachorifice 188 against the floor but at an angle that causes powder on thefloor 12 to be blown into the extraction duct 180 interior. The orifices188 are spaced along the lower edge of each rail 182 on the approachside of the extraction duct 180, thus for each rail 182 the orifices 188are provided only on one half of each respective rail but a completeline of orifices extend across the entire booth floor 16. This positivepressure air from the jet slots 188 augments the powder removal suctioncaused by the negative air pressure flow within the duct 180. Thepressurized air from the orifices 180 will tend to assist in dislodgingpowder overspray particles that may have adhered to the floor 12 andcannot be drawn up by the negative air pressure flow from the duct 180.The alternative duct 180 embodiment need not be made of the samematerials as the booth 12, however, use of such materials will result inminimal collection of powder overspray on the duct 180.

Cyclone Bypass Valve

With reference again to FIG. 3, it is sometimes desired to be able toselect whether the powder spraying system 1 operates in a powder reclaimor non-reclaim mode. For example, the system 1 may be operated in anon-reclaim mode when the powder overspray cannot be returned to thefeed center for re-use. Since the reclaim powder mode of operationinvolves the use of the cyclone system 42, it is necessary to in effecttake the cyclone 42 “off-line” for the non-reclaim mode.

FIG. 18 shows a bottom view of the bypass plenum 56. Each of the twincyclones 42 a,b have circular exhaust openings that align with openings200 and 202 in the bypass plenum 56. In the reclaim mode, exhaust airfrom the cyclones 42 a,b enters the bypass plenum 56 through theopenings 200 and 202 and passes through the plenum outlet or exhaustopening 204 to the after-filter ductwork 58. In the non-reclaim mode,the openings 200, 202 are closed off by a bypass valve assembly 206.

With reference to FIG. 3, the vertical ductwork 44 that connects theextraction duct 40 to the cyclone system 42 is connected to a plenummanifold 207 that includes a first duct 208 that is connected to thecyclone inlet 54 (keeping in mind there are two such inlets when twincyclones are used) and also includes a cyclone bypass duct 210. Thebypass duct 210 extends over the top of the cyclone system 42 and isconnected to the bypass plenum 56.

With reference to FIGS. 19A and 19B, the bypass valve 206 includes threebasic components, namely a valve door 212, seals in the form of a pairof cyclone outlet seals 214 and a bypass duct seal 216, and a valveactuator mechanism 218. The valve door 212 is disposed within the bypassplenum 56 and is therefore shown in phantom in FIGS. 19A and B, whereasthe valve actuator mechanism 218 is disposed outside the bypass plenum56. In FIG. 19A the valve door 212 is shown in the cyclone open positionand in FIG. 19B the valve door 212 is shown in the cyclone closedposition which correspond in this embodiment to the reclaim andnon-reclaim modes respectively.

The seals 214 and 216 are, for example, conventional D-seals. Thecyclone seals 214 are installed on the plenum 56 around each of thecyclone openings 200, 202. Alternatively, the cyclone seals 214 may beinstalled on the valve door 212. The bypass plenum seal 216 may also bea D-seal and is installed in the plenum 56 around the opening betweenthe bypass duct 210 and the bypass plenum 56. Again, alternatively, theduct seal 216 may be installed on the valve door 212 rather than theplenum 56 wall.

When the valve door 212 is in the upright or cyclone open position, thevalve door 212 seals and isolates the bypass duct 210 from the bypassplenum 56. The cyclone exhaust outlets are also open to the bypassplenum 56 via the openings 200, 202. As a result, the powder oversprayladen air from the extraction duct 40 passes into the cyclone inlets 54whereby much of the powder is separated from the air stream and drops tothe lower collection regions of the cyclones. The cyclone exhaust air,which may still contain powder fines, flows through the after-filterductwork 58 to the after-filter assembly 60 (FIG. 4).

When the valve door 212 is in the down or cyclone closed position (FIG.19B), the door 212 seals off and isolates the cyclone exhausts from thebypass plenum 56. The bypass duct 210 however is now open to the bypassplenum 56. When the cyclone exhausts are sealed off, the cyclone system42 is non-operational and represents a high pressure impedance to theflow of air into the cyclone inlets 54. As a result, the powder ladenair from the extraction duct 40 bypasses the cyclone inlets 54 andpasses through the bypass duct 210, then straight through the bypassplenum 56 into the after-filter ductwork 58 and finally to theafter-filter assembly or other waste receptacle.

The valve actuator mechanism 218 in this embodiment is realized in theform of a pneumatic piston type actuator 220 and a bell crank assembly222. The bell crank assembly 222 is a lever 224 that is connected at itsfree end 226 to an actuator rod 228, and at its opposite or pivot end230 is connected to the valve door 212 through the plenum 56 wall. Theactuator 220 is pivotally connected to a mounting bracket 232 so thatthe actuator 220 is free to rotate slightly to avoid binding as itpushes and pulls on the bell crank lever 224. The actuator 220 may becontrolled by the control system 48, or alternatively may be controlledby manual operation of a pressure valve. Still further, the valve door212 could be manually moved, but an actuator is preferred to assure agood seal when the door 212 is in each position.

FIGS. 20 and 21 illustrate one embodiment of the valve door 212. Thedoor 212 includes two faces 212 a and 212 b each of which will overlayrespective openings 200, 202 to seal off the cyclone 42 when the door212 is in the non-reclaim position, and cover the inlet from the bypassduct 210 when the door 212 is in the non-reclaim position. The door 212is formed of a piece of sheet metal 232 that is bent around an actuatorbar 234. One end of the actuator bar 234 is connected to the pivot end230 of the bell crank lever 224 (FIG. 19). The door 212 is enclosed atits end and top with additional sheet metal and then injected with foamfor strength and rigidity. In an alternative form of the door 212, apair of doors may be used that individually pivot to close each cycloneexhaust opening. In this alternative, a separate third door may beneeded to close off the bypass duct 210 when the system 1 is used in thereclaim mode.

It should be noted that the cyclone bypass valve concept may be used inany powder spraying system that utilizes a cyclone separator system. Thebypass valve arrangement is therefore not limited to use in a systemthat uses other aspects of the system described herein such as, forexample, the embodiments of the spray booth 10.

Powder Overspray Recovery System

With reference next to FIG. 22, the general concepts of a powderoverspray recovery system 300 is illustrated in functional schematicform. A significant aspect of the invention is that most of the powderoverspray P is extracted from the spray booth 10 and transferred back tothe feed center 46 with as little residence or dwell time as possiblewithin the various system 300 components, during a spraying operation.Thus when the need arises to changeover the color of the powder, thereis little powder remaining in the system 300 that needs to be removed.In addition, the invention contemplates various components andsubsystems within the recovery system 300 that facilitate fast cleaningand color change, as will be further explained herein.

Conceptually then, the powder recovery system 300 actually starts in thespray booth 10 wherein most of the powder overspray P falls onto thefloor 16. As previously explained herein, the booth walls or canopy 12,the top 14 and the floor 16 are preferably although not necessarily madeof non-conductive composite materials which exhibit very low adherenceof the powder. A high capacity blower 302 which in this embodiment isinstalled in the after-filter system 304, produces a large suction andattendant air flow through the twin cyclone system 42 and hence theextraction duct 40 inside the spray booth 10. The round floor 16 isrotating underneath the extraction duct 40 and thus the powder oversprayis drawn up into the extraction duct 40 and transported to the inlets 54of the cyclones 42. Although twin cyclones are used in the embodiment asa first collection device, the invention may be realized with one ormore cyclone structures. Due to the non-conductive materials of thebooth 10 and the efficient arrangement of the rotating floor 16 and theextraction duct 40, most of the powder overspray during a sprayingoperation is extracted from the booth 10.

As part of the spraying system, FIG. 22 illustrates that one or morespray guns 20 are each connected by a powder feed hose 306 to arespective powder pump 308 in the feed center 46. Each powder pump 308draws powder from a feed hopper 310 via a suction tube 312 that extendsdown into the hopper 310. The feed center 46 typically, although notnecessarily, is a separate partially enclosed booth that houses the feedhopper 310, the various pumps 308, and a purging system (not shown inFIG. 22 but described hereinafter). Although various improvements in thepumps and purging arrangement are described herein as additional aspectsof the invention, it will be readily appreciated by those skilled in theart that the basic powder recovery system of the present invention maybe realized and practiced with conventional powder feed arrangements.The basic combination of a feed hopper or powder source, suction tubes,powder pump, powder feed hose and spray gun is referred to herein as apowder application system, and thus includes elements that physicallyare installed in the powder spray booth 10 and the feed center 46, withthe feed hoses 306 being connected therebetween.

Continuing with the general description of the powder recovery system300, the cyclone system 42 separates the powder overspray P from theextraction air stream, and most of the powder is discharged from thebottom of the cyclones 42. The air is exhausted through the cycloneoutlets 42 a,b and after-filter ductwork 58. This exhaust air is sent tothe after-filter assembly 304 because the cyclones 42 cannot remove 100%of the powder, especially the very small low mass powder particlescalled fines. The after-filter system 304 is used to remove these finesbefore the air is exhausted to atmosphere.

A conventional cyclone system 42 typically would include a conicalhopper and pinch valve arrangement at the bottom of the cyclone thatcollects powder and then is periodically emptied under positive pressureback to the feed center or to waste. In accordance with a significantaspect of the invention, negative pressure is used to convey powder fromthe cyclone system to the application system or feed center 46. In oneembodiment, the conventional hoppers and valves are eliminated andreplaced with a cyclone outlet vacuum interface 314. In one embodiment,the interface 314 is realized in the form of a simple sump or transferpan with a smooth rounded interior that helps prevent powder fromaccumulating therein. The pan 314 is provided with at least one vacuuminlet connection port 356. A second outlet port 354 (not shown in FIG.22) may also be provided for connecting the interface to housekeepingvacuum and disposal.

An appropriate fitting is used at the outlet port 356 to connect theretoa vacuum line 318. The vacuum line 318 is connected at its opposite end318 a to a vacuum receiver system 320. The vacuum receiver 320 is acanister-like arrangement 322 that houses a removable filter 324. Avacuum source or pump 326 is used to produce a vacuum inside thereceiver 320 and the vacuum line 318. This vacuum draws the powder thatenters the cyclone transfer pan 314 out of the pan 314 and transfers itto the vacuum receiver 320. A portion of the powder collects on thefilter 324 while most of it falls to the receiver lower cone 328.

A positive air pressure source 330 is used to pulse the filter 324during a discharge cycle. A discharge cycle of the vacuum receiver 320is that time during which the vacuum source is shut-off for a shortperiod of time, with the filter being pulsed at that time also. At thebottom of the canister 322 is a discharge valve arrangement 332 thatopens under the force of gravity each time the vacuum pump 326 is turnedoff, allowing powder to fall into a sieve 334. In a typical system it iscontemplated that the valve 332 will open about every 30 seconds or soduring a spraying operation, but is only open for three to five secondswhile the powder falls from the cone 328 into the optional sievearrangement 334. The actual time periods and duty cycle may be varied asrequired for each system design. The sieve 334 may be a conventionalvibrating sieve that filters the powder and discharges it back to thefeed hopper 310. The short period of time, about thirty seconds, thatpowder accumulates in the vacuum receiver 320 is minimal compared toprior systems, and since it is at the end of the recovery process, hasnegligible impact on the efficiency of the recovery system 300. Theshort residence time of powder in the vacuum receiver 320 also preventsany significant accumulation of powder therein.

The vacuum receiver 320 is equipped with a releasable lid 336. Thefilter 324 is mounted on the top, so that during a color changeoperation the lid 336 is removed, what little powder is in the canister322 is blown off, and the filer replaced with another filter for thenext color. The use of color specific filters 324 speeds up the colorchange operation since such filters would be difficult to cleanautomatically. The filter in the sieve 334 is also typically a colorspecific filter that is replaced for a color change operation.

The powder recovery system 300 thus works as follows. The spray guns 20receive powder from the pumps 308 and associated hoses 306. The powderoverspray P laden air is extracted from the booth 10 and the powder isseparated in the cyclones 42. As the powder descends to the cyclonevacuum interface pan 314 it is drawn out through the vacuum line 318 andconveyed to the vacuum receiver 320 where it is separated from thevacuum source and discharged to the sieve 334 and the back to the feedhopper 310. Thus, most of the powder overspray P is in near continualmotion from the moment it leaves the gun 20 spray nozzle to the time itis returned to the feed hopper. The brief period of time that powder isaccumulating in the vacuum receiver 320 permits the use of a powderconveyance arrangement having much less surface area, permitting muchfaster cleaning times than is realized by prior art systems that usesurge hoppers, pinch valves and so forth that are connected to thecyclone. During a spraying operation, very little powder remains withinthe spray booth 10, the cyclones 42 or the receiver 320 subsystems.

It is noted that the various aspects of the vacuum recovery system andfeed center in accordance with the invention may alternatively be usedwith other spray booth and powder extraction designs, and thus are notlimited to use with the exemplary spray booth and extraction ductconcepts. For example, various aspects of the recovery system and feedcenter may be used with a cartridge filter type extraction system.

Cyclone Vacuum Interface

With reference to FIGS. 23, 24, 25 and 25A, the twin cyclone system 42includes the side-by-side tangential inlets 54 a,b and separate cycloneexhaust ports 42 a,b. Each cyclone 42 also has a lower recovery cone 350a,b. The cyclone vacuum interface unit 314 in this embodiment isrealized in the form of a sump or transfer pan 352 that is hinged ontothe bottom of the twin cones 350 a,b and secured by any suitable latchmechanism to allow easy opening of the pan 352 for cleaning. Thedirectional arrows in FIG. 24 represent how the swirling powdergenerally moves within the interface 314 as the powder exits thecyclones. This swirling is a result of the air flow pattern in thecyclone and helps direct powder to the outlet ports 354, 356.

The vacuum interface 314 includes at least one outlet port 354, andpreferably a second outlet port 356. Each port is a tubular structurethat opens generally along or adjacent to the bottom surface 358 to forma smooth seamless outlet passageway 360 for the powder. As illustratedin FIG. 25A, each outlet port 354, 356 is generally circular incross-section but at the opening to the pan 352 interior is formed intoa wider rectangular cross-section 351. Other cross-sectional areas suchas an ellipse could be used as required. The rectangular cross-sectionalopening 351 has the same cross-sectional area as the round port 354, 356but is more efficient in collecting powder from the pan 352 due to theswirling pattern of the powder as it enters the pan 352 from the cyclonelower cones 350 a and 350 b. This is because, as illustrated by thedirectional arrows in FIG. 24, the powder tends to sweep laterallyacross the pan 352 interior rather than coming straight down into theoutlet ports 354, 356. Thus, a wider opening 351 with no lesscross-sectional area of the opening as compared to the tubular port 354,356 allows more time for the powder to be swept up by the same energy ofthe vacuum in the outlet port.

The lower cones 350 a and 350 b of the twin cyclones are provided withaccess doors 351 a and 351 b that facilitate cleaning of the cyclonesduring a color change operation.

One of the outlet ports 356 is connected to the vacuum line 318 by anappropriate compression fitting (not shown) or other suitableconnection. Powder is thereby conveyed from the pan 352 to the feedcenter 46 by being drawn into the vacuum receiver 320. When used, thesecond port 354 may be connected to another suction line that sends thepowder to a waste collection area.

Vacuum Receiver Unit

With reference to FIGS. 26-28, the vacuum receiver 320 includes the maincanister body 322 having an integral lower conical collection portion328. The vacuum receiver 320 is, in accordance with one aspect of theinvention, installed in the feed center 46 (FIG. 22). In thisembodiment, the canister 322 includes opposed trunion-style transversemountings 362. The tunnions 362 are pivotally mounted in the feed center46 to allow the vacuum receiver to be rotated about an axis VR at least90 degrees such that the top end of the receiver 320 is about atshoulder facing height with the canister oriented in a generallyhorizontal position. This allows an operator, after removing thecanister lid 336, to blow off powder through the inside of the canister322 towards a powder collection diffuser wall (382 a) in the feed center46 structure.

The canister 322 includes a series of latches 364 that secure thecanister lid 336 to the canister body 322. The lid 336 also supports apowder filter 324 so that the filter can easily be changed by simplylifting off the lid 336 from the canister 322. The lid 336 furtherincludes a connection 366 for the vacuum line 327 (FIG. 22). An air lineconnection 368 is also provided. The lid 336 further retains a pulsevalve 370 that is used to apply high pressure air from the positivepressure source 330 to the filter 324 during a powder discharge periodto dislodge powder from the filter 324.

At the lower end of the canister 322 is a valve actuator assembly 372.FIG. 27 shows the valve plate 332 open and FIG. 28 shows the valve plate332 closed. The valve plate 332 is held closed when the plate 332 is inits raised or closed position whenever there is a vacuum within thereceiver 320. When the vacuum is periodically interrupted, the valveplate 332 drops down by gravity into the open position illustrated inFIG. 27 and powder inside the receiver 320 is discharged to the sieve334.

An air actuated cam wheel 374 engages the underside of the valve plate332. This wheel 374 is moved into engagement with the valve 332 by anair actuator 376. The air actuator 376 has an appropriate fitting 378connected to a positive pressure air line (not shown). When pressurizedair is supplied, the wheel 374 is rotated up into engagement with thevalve 332 and closes the valve 332 against the bottom of the canister322. When the vacuum is present in the receiver 320, the air pressure atthe actuator 376 may be released as the vacuum alone will maintain thevalve 332 shut and tightly sealed. An appropriate seal may be usedaround the bottom of the receiver 320 or other sealing mechanisms may beused as required. Periodically the vacuum is interrupted and the valve322 falls open under the force of gravity, discharging any powder in thecanister 322 into the sieve assembly 334. The control system 48 may beused to automatically time the vacuum interruption cycle and theactuator 376.

The canister 322 also includes a tangential opening 380. The outlet end318 a of the vacuum line 318 (FIG. 22) is connected to this opening 380by any suitable device such as a re-usable compression fitting (notshown). With the rather rigid vacuum line 318 connected to the receiver320, the receiver 320 will remain in its vertical orientation without aseparate latching device, although a separate latching device may beused if required.

Cyclone Efficiency

With reference to FIG. 22 and the above discussion relating to thecyclone vacuum interface and the vacuum receiver unit, an importantaspect of the present invention relates to the influence or effect thatthe negative pressure has at the cyclone outlet port 356. It isimportant to note that this aspect of the invention is not necessarilydependent on the particular vacuum interface arrangement at the cycloneoutlet nor on the particular embodiments described herein with respectto the vacuum receiver 320, the vacuum source 326, the sieve 334 or thehopper/container 310. In other words, the concept of improving cycloneefficiency may be realized in many different ways of applying a negativepressure to a cyclone or twin cyclones or multiple cyclones having asingle common outlet. By outlet is simply meant an area or region wherethe negative pressure can be presented to an extraction point to recoverpowder separated by the cyclone. The cyclone outlet may be aconventional truncated cone arrangement that is commonly found withcyclonic separators, or may be the realized in the form of the transferpan 352 described herein. Other cyclone outlet vacuum interfacearrangements may be conveniently used as required. The important aspectis that the interface arrangement permit a negative pressure and inducedair flow to be presented at the outlet area of the cyclone to conveypowder back to a container.

As noted in the Background of the Invention herein, some customerscannot or do not want to use larger cyclones, particularly tallcyclones. Heretofore, such customers would sacrifice cyclone efficiencyin order to be able to use a shorter cyclone. In accordance with theinvention, apparatus and method are provided to influence cycloneefficiency so that high cyclone efficiency is realized even with cyclonearrangements having smaller aspect ratios.

Cyclone efficiency is related to the aspect ratio, static pressure andair volume at the inlet to the cyclone. Shorter, lower aspect ratiocyclones produce a higher static pressure for a given air volume andhave a lower efficiency due in part to the lower aspect ratio. Inaccordance with one aspect of the invention, by applying a negativepressure at the cyclone outlet, powder that is separated from the airstream by cyclonic activity can be conveyed to a container, such as thereceiver 320. The negative pressure induces an air volume that entrainspowder at the cyclone outlet and conveys it to the container. Powder atthe cyclone outlet is of course swirling and moving. The negativepressure is characterized by a “zone of influence” or a finite region inwhich powder can be “captured” out of the cyclonic flow and entrainedinto the induced air volume for conveyance to the container. It is notsimply a matter, however, of connecting a vacuum source to the cycloneoutlet. In order to convey powder from the cyclone 42 to the container(such as the receiver 320 for example), there must be a sufficient airvolume or flow to entrain the powder and draw it away from the cycloneoutlet and convey it to the container. If the induced air flow is toolow relative to the static pressure in the cyclone, then powder will notbe conveyed to the container, and in some cases the cyclone can actuallydraw powder back from the container (keeping in mind that the cyclone isactually also a source of negative pressure within the system).

It is noted that prior art cyclone efficiency is typically on the orderof 90-92%. By implementing the present invention, efficiency of therecovery system can be realize on the order of 97-98% or higher and thiscan represent a tremendous savings in terms of recovered powder. As usedherein the term “cyclone efficiency” refers to the ratio of powderyielded from the cyclone versus the amount of powder that enters thecyclone inlet.

Accordingly, it is an important aspect of the invention that the vacuuminduced air volume complement the static pressure profile of thecyclone. In other words, the induced air volume should have apredetermined relationship with respect to the static pressure profileof the cyclone. This predetermined relationship may be empiricallydetermined for each cyclone recovery system having a set of operatingparameters (i.e. cyclone size and exhaust air volume). For each systemconfiguration, empirical analysis may be used to determine an optimalrelationship between the cyclone static pressure and the vacuum pumpinduced air volume so that the negative pressure presented at thecyclone outlet recovers powder from the outlet and conveys the powder tothe container. This assures a maximum yield of powder in the containerrecovered from the cyclone that otherwise would be lost out the cycloneexhaust. As a general example, when a cyclone is used that has a higherstatic pressure such as occurs with a lower aspect ratio cyclone, thevacuum source is selected to produce a related increase in the inducedair volume. It should be noted that this enhanced recovery approach isderived from the pressure capabilities of the vacuum pump that generatethe induced air volume. In general the induced air volume in most caseswill not exceed 1% of the cyclone exhaust air volume.

As an example, when a shorter, smaller aspect ratio cyclone is used, thestatic pressure may increase from about 6 inches of water column(typical of a higher aspect ratio cyclone) to about 8 or 9 inches ofwater column. In such a case, a vacuum source 326 should be used thatcan provide an induced air volume of at least 100 cfm (cubic feet perminute) at the location where the negative pressure is presented to thecyclone outlet. In the exemplary pump (model no. MLL 400 available fromPIAB), 100 cfm corresponds to about 3 inches of mercury. This willassure that powder will be drawn away from the cyclone outlet andconveyed to the container so as to significantly increase the yield ofpowder in the container that would otherwise be lost through the cycloneexhaust. As another example, an induced air volume of 40 cfm at 0.9inches of mercury would be just as effective as 70 cfm at 6 inches ofmercury when applied against a cyclone exhaust volume of 11,250 cfm at 7inches water column static pressure. Using an appropriate predeterminedrelationship between induced air volume from the vacuum source and thecyclone static pressure, cyclone efficiency as measured by yield ofproduct at the container can be on the order of about 97-98%. Again inthis example the induced air volume is no greater than 1% of the exhaustair volume of the cyclone. The remaining 2% or so is loss primarily dueto fines and other very small particles that routinely do not travel allthe way to the bottom of the cyclone prior to being taken up through theexhaust core. The exemplary numbers herein should not be construed in alimiting sense but rather are used to illustrate what is meant by apredetermined relationship between a characteristic of the cyclone (inthis example the static pressure) and a characteristic of the vacuumsource (in this example the induced air flow). Other parameters for apredetermined relationship may be available to establish sufficientinduced air volume to recover powder from a particular cyclone.

In the specific exemplary embodiments herein, it is important that thereceiver 320 be periodically emptied, because if it fills with too muchpowder, the induced air volume may drop too low and actually cause astall in the conveyance of powder from the cyclone 42 to the receiver320.

Because maximum efficiency is realized with a good match between thecyclone static pressure and the vacuum source induced air volume, it ispreferred that the vacuum source be couple to the cyclone outlet by anair-tight coupling arrangement. In the exemplary embodiment this isrealized by way of the receiver 320, the vacuum line 318 and the airtight coupling between the vacuum line 318 and the cyclone outlet 356 ofthe pan 352. Again, the particular outlet configuration of the cycloneis not a critical feature to realize the benefits of the presentinvention.

Thus, with use of a negative pressure at the outlet of a cycloneseparator, cyclone efficiency and yield of product conveyed from thecyclone to a container can actually be maintained and compares veryfavorably to a high efficiency cyclone (e.g. one with a higher aspectratio) even in a lower aspect ratio cyclone arrangement. A customertherefore can use smaller cyclones that reduce noise and energyconsumption and have a lower profile without an attendant loss inefficiency.

Feed Center

With reference to FIG. 29, the feed center 46 includes a wall structure382 that partially encloses the feed hopper 310. The back wall 382 a ispreferably a diffuser wall that has a series of through holes (notshown). The wall forms part of a suction plenum behind the feed center46, and a blower 340 draws powder from the interior of the feed center46 through the back wall 382 a and into a collection device or a powderwaste disposal. In this manner, various components within the feedcenter 46, such as, for example, the suction tubes 312, the receiver 320interior, the receiver lid 336, the pumps 308 and so forth, may becleaned with air wands to remove excess powder during a color changeoperation, usually after the hopper 310 has been withdrawn from the feedcenter 46.

In FIG. 29 the pump suction tube array 312 (in the embodiment describedherein there are a plurality of pumps and guns, however, any number ofpumps and guns may be used as required) is illustrated in a raisedposition such as would be the case initially during a powder changeover.The pumps 308 and suction tubes 312 are supported on a pump frame 384(FIG. 30) that is raised and lowered by operation of a pneumaticcylinder 386 or other suitable linear translator. The frame 384 slidesalong a set of rails 392. A feed hose manifold 385 is used to connectall the feed hoses to their respective pumps 308 by installing the hosemanifold on top of the pump frame 384.

The vacuum receiver 320 is mounted on the trunnions 362 which arepivotally supported on two legs 388 which are mounted on and extenddownward from the ceiling or top 382 b of the feed center wall structure382. The sieve assembly 334 includes a powder filter 335 typically inthe form of a screen mesh. The sieve 334 is mounted just below thevacuum receiver 320 and includes a discharge chute 390 that dischargesfiltered powder from the sieve to the feed hopper 310. The screen filter335 is typically color specific and changed for each color changeoveroperation, as is the vacuum receiver 320 filter.

FIG. 30 illustrates additional features of the powder feed center 46arrangement. The pump frame 384 is supported on a pair of rails orcarriage 392 under the control of the actuator 386. An air tube diffuser394 is supported below the bottom ends of the suction tubes 312 andsupplies fluidizing air into the feed hopper 310 during a sprayingoperation. It should be noted that the term “feed hopper” should bebroadly construed as including any suitable container for the powder,including but not limited to the powder bag. By providing a fluidizingair mechanism with the suction tubes, there is no need for a fluidizinghopper, and powder may be pumped directly from the original powdercontainer. The vacuum connection 327 between the vacuum receiver 320 andthe vacuum pump 326 is also illustrated in FIG. 30. A vacuum inlet 327 a(see FIG. 29) is provided in the receiver top cover 336.

FIGS. 30 and 32 also schematically show a pump and gun purge manifoldsystem 396. The purge manifold system 396 is an array of air nozzles orvalves “PA” that are installed in the lower portion of the feed center46 and may, for example, fit under the hopper 310 even when the hopper310 is positioned in the feed center 46. These nozzles correspondinglyengage the lower end of the suction tubes 312 when the tubes 312 arelowered into purge position by the operation of the pneumatic cylinder386. This is done as part of the color change operation and/or a gun andpump purge operation. In either case, the pumps 308 and suction tubes312 are lowered into engagement with the purge system 396. FIG. 30 showsan intermediate lowered position G of lower portion of the tube array312 as it is lowered into engagement with the purge system 396. FIG. 32illustrates the suction tubes 312 lower ends engaged with the purgemanifold 396. Once the suction tubes 312 are connected to the purgesystem 396, pressurized air through an air line 395 is forced throughthe pumps 308, and the guns 20 to purge them of powder. Although thepurge operation may also purge the feed hoses 306, it is also a commonpractice to change the feed hoses for a light to dark or dark to lightcolor changeover as the hoses can be difficult to completely purge.

In accordance with another aspect of the invention, a powder pump 308provides a powder flow path therethrough that is straight and “in-line”,thereby eliminating any ninety degree or other turns within the pump308. By “in-line” is meant that powder flows straight through the pump308 from inlet to outlet on a single axis. FIG. 31 illustrates apreferred embodiment of the powder pump 308 in accordance with thisaspect of the invention. In this embodiment, each pump 308 has anin-line pump. Each pump 308 includes a suction tube end 400 that slidesinto the top end of its respective suction tube 312. Each pump 308 alsoincludes appropriate fittings 402 for atomizing and flow air. Whenpressurized air enters the pump 308, a suction is created in the suctiontube 312 that draws powder from the hopper 310 into the pump 308. Thepump 308 discharges the powder through an outlet 404 which may be, forexample, a nipple that receives one end of a powder feed hose 306. Theother end of the feed hose is connected to the corresponding spray gun20 in the spray booth 10. The preferred design of the pump is optimalfor color change operations. Because of the “in-line” structure, thepowder flow does not have to make a ninety degree turn within the pumpas would occur in a conventional powder pump. This permits the pump tobe purge cleaned by compressed air of any residual powder much morequickly and easily than in prior pump designs. Although this preferredembodiment of the in-line pump is highly advantageous, the presentinvention is not limited to the use of this in-line pump and any pumpmay be used as required.

With reference to FIGS. 33 and 34, the in-line pump concept exemplifiedin FIG. 31 may be used in combination with a straight through in-linespray gun concept. By providing a powder pump that has a straightthrough powder flow path, especially without any ninety degree or othersignificant turns in the flow path, and a straight through spray gun, anapplication system in accordance with this aspect of the inventionachieves a flow of powder from the feed hopper 310 to a spray gun (410)spray nozzle (410 a) without any sharp turns in the flow path. In priorsystems, the powder pump and/or spray gun typically include one or moreninety degree turns.

In the embodiment of FIG. 33, an in-line pump 400 is submerged in thepowder P within a feed hopper 310. The pump 400 is, for example,positioned within a tube 401 that extends down into the hopper 310. Thetube 401 includes appropriate fittings connected to an atomizing airsupply 406 and a flow air supply 408. Powder is drawn up into the tube401 from the bottom thereof. Fluidizing air may be supplied as required,or supplied via the tube 401 as described hereinbefore.

A powder feed hose 306 is connected at one end to the outlet of the pump400 and at an opposite end to a powder inlet such as a feed tube of aspray gun 410. In one embodiment of the straight through spray gun 410,a gun such as described in co-pending U.S. patent application Ser. No.09/667,663 filed on Sep. 22, 2000 for POWDER SPRAY GUN and Ser. No.09/490,099 filed on Jan. 31, 2000 for POWDER SPRAY GUN, may be used, theentire disclosures of which are both fully incorporated herein byreference. Such a gun design is characterized in part by a single axisin-line powder flow path 412 from the gun inlet end through the nozzle410 a.

FIG. 34 illustrates an alternative embodiment of this aspect of theinvention. In this embodiment, the pump 400 may be mounted on top of thefeed hopper 310, rather than within the feed hopper. A suction tube 414extends from the pump 400 down into the powder P. All other aspects ofthe embodiment of FIG. 34 may be the same as in FIG. 33.

FIG. 36 illustrates another alternative embodiment of the in-line pump400. In this example, the atomizing section 450 is axially separatedfrom the flow air section 452 by a tubular extension 454. This permitsthe atomizing air function to be performed outside of the powder supplyor at the spray gun.

Note in FIG. 31 that powder may be drawn axially up into the pump 400 asillustrated by the arrows 460 (FIG. 33). Alternatively, or in additionto the axially in flow of powder, the tube 401 may be provided withlateral openings 462 that allow the powder to enter the tube 401 fromthe side. This alternative arrangement may in some applications allowthe submerged pump to be installed closer to the bottom of the feedhopper 310 or bag to pump out most of the powder therein.

The pump design 400 of FIG. 31 is one example of an in-line pump designthat is suitable for the embodiments of FIGS. 33 and/or 34. The pump 400includes a housing 420 within which are slip-fit inserts 422 and 424.These inserts 422, 424 define an axially tapered powder flow path 426.The inserts 422, 424 also define an air annulus 428 that is in flowcommunication with the flow air inlet 408. The flow air passes into anangled and constricted air jet 430 that is angled forwardly toward thepump outlet 404. The air jet 430 opens to the powder flow path 426 at anopening 432.

When pressured air is supplied to the flow air inlet 408, the resultanthigh velocity air flow into the flow path 426 creates a substantialnegative pressure relative to the fluidized powder in the feed hopper310. Powder is therefore drawn up into the pump 400 and transferred outto the feed hose 306 and spray gun 410,20.

The forward insert 424 defines an atomizing air passageway 434 that isin flow communication with the atomizing air inlet 406. The atomizingair passes into an angled and constricted air jet 436. The atomizing airjet 436 opens to the powder flow path 426 at an opening 438 that isdownstream of the flow air opening 432. The atomizing air assists infurther breaking up of the powder into smaller particles. Atomizing airis not always required, however. Still further, atomizing air may beprovided at the spray gun rather than at the pump.

We have discovered that the use of an in-line pump, such as a pumpillustrated in FIG. 31 for example, produces a more consistent filmthickness across a wider area of the object being sprayed, as contrastedwith a conventional powder pump that forces the powder to turn ninetydegrees or so within a pump. This effect is illustrated in arepresentative manner in the graph of FIG. 35. This graph illustratesthe relationship between film thickness across a width of the sprayedobject for a conventional right angle pump (Graph A) and an in-line pump(Graph B) in accordance with the invention. Note that the thickness ismore uniform over a wider area “C” for the in-line pump applicationsystem. This effect is further pronounced when the application systemuses an in-line pump and a straight through gun as describedhereinbefore.

The exemplary system 1 (FIG. 22) thus provides an arrangement by whichpowder overspray is scavenged on a real-time continuous basis from thespray booth 14 to a first collection device in the form of a cyclonesystem 42, and conveyed back to the feed center/application system 46 ona real-time near continuous basis. The powder is continually scavengedfrom a cyclone transfer pan so that the powder does not dwell within therecovery system until it reaches a vacuum receiver near applicationsystem feed hopper. The powder has a minimal dwell time within thevacuum receiver 320, and the vacuum receiver 320 presents a minimalsurface area and volume to clean compared to prior art systems that usepositive air pressure to reclaim powder through a cyclone surge hopperand pinch valve arrangement.

Color Changeover Procedure

A description of an exemplary color change procedure will now beprovided. The specific order of the steps and the number and procedureof the steps are not necessarily required in all cases depending on theoverall spraying system 1 design. For the exemplary spraying system 1embodiment described herein, it is contemplated that a complete colorchangeover can be effected with only two operators, one primarilycleaning the booth 10 and cyclone 42, while the other primarily cleansthe feed center 46. A single operator could alternatively be used ormore operators if so required. In a prototype system, two operators areable to do a complete color change procedure in only about five minutes.Typical known systems are on the order of 15 minutes or more, with someas long as 45 minutes, and these other systems require much morecumbersome and less reliable clean out procedures.

When a color change procedure is to be performed, the oscillators 26 arestopped and the gun movers 24 move the guns 20 to the home position. Thefeed center sieve 334 stops vibrating and the fluidizing air to thehopper 310 is also stopped. The suction tubes 312 are raised out of thehopper 310 and the gun movers 24 retract the guns to a position outsidethe booth 10. The gun bodies are blown off as they are retracted.Positive air pressure directs the powder into the booth 10 where itpasses into the extraction duct 40. All of these steps may be performedautomatically under control of the main control system 48. One of theoperators removes the feed hopper 310 from the feed center 46.

The feed center operator disconnects the vacuum line 318 from thecyclone collection pan 314, and blows off what little powder remains inthe pan 314. Note that at all times the after-filter 304 system isoperational so that any powder blown off the pan 314 is drawn up intothe cyclone and exhausted to the after-filter 304. When the pan 314 isopen, any powder from the extraction duct 40 also passes straight intothe cyclone exhaust to the after-filter 60, because with the pan openthe cyclones 42 are non-operational as separators.

With the vacuum pump 326 still on, the operator inserts one or morecleaning devices into the cyclone end of the vacuum line 318. Forexample, a foam cylinder or other spongy or soft body may be used. Thecleaning device is pulled through the vacuum line 318 by the vacuumsuction and exits inside the vacuum receiver 320. Several cleaningdevices can be sent through the line 318 to assure thorough cleaning.Preferably the line 318 is a smooth walled seamless structure such asstainless steel or aluminum tubing.

Next the guns 20 and pumps 308 are purged. The control system 48 lowersthe suction tube array 312 via the pump support frame 384 onto the purgemanifold 396, sends purge air pulses through the suction tubes 312, thepumps 308, the hoses 306 and the guns 20. This powder from the purgingis swept up into the extraction duct 40. After purging the suction tubes312 and pump support frame 384 are raised. The outsides of the suctiontubes 312 are blown off and the booth operator blows off the door 150seams from outside the booth 10. The control system 48 is theninstructed to stop the floor 16 rotation and raise the floor 16 to itssealed position against the bottom of the canopy 12. The booth operatorcan enter the booth 10 and walk on the floor. Using a pressurized airwand, the operator blows what little powder is on the booth walls andceiling down onto the floor 16. The operator also blows powder off theextraction duct 40. After complete blow-off, the operator exits thebooth 10, and the control system 48 is instructed to lower the floor 16to its rotation position, and the blown-off powder is extracted to thecyclone system 42. At this time the seal blow-off valve 80 is alsoactivated to completely blow powder off the seal 104 and draw powder offthe floor 16 portion that extends outside the perimeter of the canopy 12walls. The booth is thus completely purged of powder.

The vacuum receiver 320 is designed so as to rotate about the axis VRwhereby the top of the canister 322 is about shoulder height and facingthe feed center operator. The vacuum pump line 327 is disconnected fromthe canister top 336, as is the pulse air line from the positivepressure source 330. In this position, the operator can easily rotatethe receiver 320 so that the lid 336 is facing the operator (i.e. facingthe front of the feed center 46). The operator unlatches and removes thelid 336 and removes the color specific filter 324. The cleaning spongesare also removed. The operator then blows off the canister 322 interior,the lid 336 and related parts.

The sieve 334 top section is removed and the color specific filterscreen 335 is removed. If a similar shade (light to light or dark todark) color will be next used, the sieve screen 335 is blown off. If adifferent shade will be used next, the screen is set aside for latercleaning. The sieve 334 is then cleaned and the proper screen 335installed. Another color-specific filter 324 specific to the next colorbeing sprayed is then mounted on the lid 336 and inserted into thecanister 322. The lid 336 is re-latched and the canister 322 swung backto its vertical position (as shown in FIG. 22). The vacuum lines 318 and327 are then reconnected to the receiver 320 and the pulse air line isalso reconnected. While the feed center sieve and vacuum receiver arebeing cleaned, the other operator has opened access doors in the cyclonelower cones 350 a and 350 b and blows off all interior surfaces of thecyclones and any powder remaining in the pan 314.

Next the feed hose manifold 385 is removed and another manifoldinstalled for the next color. The other ends of the new feed hoses areconnected to the spray guns 20.

Another feed hopper 310 that contains the next color powder coating tobe sprayed is then installed into the feed center 46 and the suctiontubes and pumps 308 lowered into operational position. Lastly, thecyclone doors are closed, the collection pan 314 closed and the vacuumline 318 reattached to the collection pan 314. This completes theexemplary color change operation.

It will be readily appreciated that the color change procedure isgreatly facilitated by the efficiency and thoroughness by which powderoverspray is removed in a real-time manner from the booth 10 during aspraying operation due to the interaction between the rotating floor 16and the overlaying extraction duct 40. However, the vacuum conveyancefeature of the present invention, which conveys powder from the cyclonesystem 42 to the feed center/application system, may be used with anypowder extraction and spray booth arrangement, including a cartridgefilter type collection system.

It is intended that invention not be limited to the particularembodiments and alternative embodiments disclosed as the best mode orpreferred mode contemplated for carrying out the invention, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. Powder recovery apparatus for a powder coating spray system,comprising: a powder spray booth; a cyclone having an inlet thereto thatreceives powder entrained in air from said spray booth wherein saidcyclone operates to separate powder from the air; said cyclone having anoutlet for recovering said separated powder and an exhaust for air; anda negative pressure source coupled to said cyclone outlet; said negativepressure source producing an induced air volume that causes asubstantial flow of powder from said cyclone outlet to a container toreduce powder lost through said cyclone exhaust.
 2. The apparatus ofclaim 1 wherein said cyclone operates at a static pressure and saidnegative pressure source produces an induced air volume that issufficient to draw powder from said cyclone outlet to optimize powderrecovery.
 3. The apparatus of claim 1 wherein said negative pressuresource comprises a vacuum pump.
 4. The apparatus of claim 3 wherein saidvacuum pump is coupled to said container; said container being coupledto said cyclone outlet.
 5. The apparatus of claim 4 wherein saidcontainer comprises a receiver having a filter that separates powderfrom said induced air flow.
 6. The apparatus of claim 5 wherein saidreceiver is coupled to said cyclone outlet by a pipe.
 7. The apparatusof claim 6 wherein said vacuum pump, receiver and pipe provide a closedair-tight system coupling the cyclone outlet to said negative pressuresource.
 8. The apparatus of claim 1 comprising a blower coupled to saidexhaust to draw said powder entrained air into said cyclone at saidcyclone inlet, said blower comprising a filter that separates powderfrom exhaust air.
 9. The apparatus of claim 1 wherein said cycloneoperates at a static pressure of at least 7 inches water column and saidnegative pressure source produces an induced air volume of at least 95cfm.
 10. A method for influencing efficiency of a cyclonic separator ofthe type having an inlet that receives powder coating particlesentrained in an air flow, an outlet for recovering powder separated fromthe air flow, and an exhaust coupled to a blower that produces thepowder entrained air flow into the cyclone at the cyclone inlet; themethod comprising: applying negative pressure at the cyclone outlet toconvey powder particles from the cyclone outlet to a container, saidnegative pressure being sufficient to yield powder particles in saidcontainer that would otherwise pass through the cyclone exhaust in theabsence of said negative pressure.
 11. The method of claim 10 whereinsaid negative pressure produces an induced air volume sufficient toentrain powder particles at the cyclone outlet and transfer saidentrained particles to said container.
 12. The method of claim 10wherein the cyclone operates at a static pressure defined between aninlet region and exhaust region thereof; said induced air flow having apredetermined relationship with respect to said static pressure torecover powder from the cyclone outlet and convey said powder to saidcontainer.
 13. The method of claim 10 wherein said negative pressure isprovided by a vacuum pump that is coupled to the conveyor outlet via aclosed air-tight system.
 14. The method of claim 13 wherein said vacuumpump produces an induced air volume of at least 90 cfm.
 15. The methodof claim 14 wherein the cyclone is operated at a static pressure of atleast 6 inches water column.
 16. Apparatus for increasing efficiency ofa cyclone separator used to recover powder from a powder coating system,comprising: a cyclone having an inlet thereto that is adapted to receivepowder entrained air wherein said cyclone operates to separate powderfrom the air; said cyclone having an outlet for recovering saidseparated powder and an exhaust for air; and a negative pressure sourcecoupled to said cyclone outlet; said negative pressure source producingan induced air volume that causes a substantial flow of powder from saidcyclone outlet to a container to reduce powder lost through said cycloneexhaust.
 17. The apparatus of claim 16 wherein said cyclone operates ata static pressure and said negative pressure source produces an inducedair volume that is sufficient to draw powder from said cyclone outlet tooptimize powder recovery.
 18. The apparatus of claim 16 wherein saidnegative pressure source comprises a vacuum pump.
 19. The apparatus ofclaim 18 wherein said vacuum pump is coupled to said container; saidcontainer being coupled to said cyclone outlet.
 20. The apparatus ofclaim 19 wherein said container comprises a receiver having a filterthat separates powder from said induced air flow.
 21. The apparatus ofclaim 20 wherein said receiver is coupled to said cyclone outlet by apipe.
 22. The apparatus of claim 21 wherein said vacuum pump, receiverand pipe provide a closed air-tight system coupling said cyclone outletto said negative pressure source.
 23. The apparatus of claim 16 whereinsaid cyclone operates at a static pressure of at least 7 inches watercolumn and said negative pressure source produces an induced air volumeof at least 95 cfm.
 24. The apparatus of claim 16 wherein said negativepressure source produces an induced air flow based on the staticpressure of said cyclone.
 25. The apparatus of claim 24 wherein saidnegative pressure source is selected to produce an increased induced airflow in relation to an increase in said static pressure.
 26. Apparatusfor increasing efficiency of a cyclone separator used to recover powderfrom a powder coating system, comprising: a cyclone having an inletthereto that is adapted to receive powder entrained air wherein saidcyclone operates to separate powder from the air; said cyclone having anoutlet area for recovering said separated powder and an exhaust for air;said cyclone having a static pressure value associated therewith; and anegative pressure source coupled to said cyclone outlet area; saidnegative pressure source producing an induced air volume that causes asubstantial flow of powder from said cyclone outlet area to a containerto reduce powder lost through said cyclone exhaust; said induced airflow having a predetermined relationship with respect to said staticpressure.
 27. A method for increasing efficiency of a cyclonic separatorof the type having an inlet that receives powder coating particlesentrained in an air volume, an outlet area for recovering powderseparated from the cyclone air, and an exhaust; the method comprising:applying negative pressure at the cyclone outlet area to recover powderparticles from the cyclone outlet area and to convey the recoveredpowder particles to a container, said negative pressure producing aninduced air volume having a predetermined relationship with respect to astatic pressure characteristic of the cyclone to yield powder particlesthat would otherwise pass through the cyclone exhaust in the absence ofsaid negative pressure.